Organic light emitting display device having layer to control charge transfer

ABSTRACT

Discussed is an organic light emitting display device. The organic light emitting display device may include an anode on a substrate, a first emission part that is disposed on the anode and includes a first emission layer and a first electron transfer layer, a second emission part that is disposed on the first emission part and includes a second emission layer and a second electron transfer layer, and a cathode on the second emission part. At least one among the first electron transfer layer and the second electron transfer layer may include a first material and a second material, and an absolute value of a LUMO energy level of the first material may be larger than an absolute value of a LUMO energy level of the second material.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of the Korean PatentApplication No. 10-2015-0162862 filed on Nov. 19, 2015, and No.10-2016-0067756 filed on May 31, 2016, all of which are herebyincorporated by reference as if fully set forth herein.

BACKGROUND Field

The present disclosure relates to an organic light emitting displaydevice, and more particularly, to an organic light emitting displaydevice with enhanced lifetime.

Discussion of the Related Art

Recently, as society advances to the information-oriented society, thefield of display devices which visually express electrical informationsignals is rapidly advancing. Various display devices, having excellentperformance in terms of thinness, lightness, and low power consumption,are being developed correspondingly.

Examples of the display devices include liquid crystal display (LCD)devices, plasma display panel (PDP) devices, field emission display(FED) devices, organic light emitting display devices, etc.

Particularly, the organic light emitting display devices areself-emitting devices. In comparison with other display devices, theorganic light emitting display devices have a fast response time, highemission efficiency, high luminance, and a wide viewing angle and thusare attracting much attention.

An example of a white organic light emitting device is discussed inKorean Patent Application No. 10-2009-0092596 (published as KR2011-0035048).

SUMMARY

Accordingly, the present disclosure is directed to provide an organiclight emitting display device that substantially obviates one or moreproblems due to limitations and disadvantages of the related art.

Organic light emitting devices each include an emission layer which isformed between two electrodes. An electron and a hole are injected fromthe two electrodes into the emission layer, and an exciton is generatedby combining the electron with the hole. The organic light emittingdevices are devices based on the principle that light is emitted whenthe generated exciton is dropped from an excited state to a groundstate.

A hole transport layer or an electron transport layer may be providedfor injecting the electron and the hole into the emission layer includedin the organic light emitting device. Since the electron transport layeris a layer that plays an important role in adjusting a balance ofelectrons and holes, the electron transport layer is formed of amaterial, which is high in electron mobility, for enabling an electronto be smoothly injected and lowering a driving voltage.

In a case where the electron transport layer uses a material which ishigh in electron mobility, since an electron is quickly transferred tothe emission layer, the driving voltage does not increase, but it isdifficult to adjust a balance of electrons and holes in the emissionlayer. Therefore, a recombination zone or an emission zone where anexciton is generated is not formed in the emission layer but is providedin an interface between the hole transport layer and the emission layer.Accordingly, the emission layer cannot contribute to emit light, causinga reduction in lifetime of the emission layer. Also, when an emissionzone of the emission layer is narrowed as time elapses, lifetime isfurther reduced.

Moreover, in a case where the electron transport layer having lowelectron mobility, since a balance of holes and electrons is adjusted,lifetime of the electron transport layer is enhanced, but as timeelapses, lifetime of the electron transport layer reduced rapidlyinstead of gradually.

Therefore, the present inventor recognizes the above-described problemsand has done various experiments for improving a lifetime of an organiclight emitting display device by adjusting an electron mobility of anelectron transport layer for optimizing a charge balance of an emissionlayer.

Through the various experiments, the inventor has invented an organiclight emitting display device in which an electron transport layer isformed of materials which have different absolute values in a lowestunoccupied molecular orbital (LUMO) energy level, and a balance ofelectrons and holes in an emission layer is maintained by adjusting acontent of the materials so as to enhance a lifetime of the organiclight emitting display device, thereby enhancing lifetime. Also, theinventor has invented an organic light emitting display device in whicha balance of electrons and holes in an emission layer is maintained byadjusting an energy bandgap of an electron transport layer and an energybandgap of a charge generation layer adjacent to the electron transportlayer so as to enhance a lifetime of the organic light emitting displaydevice, thereby enhancing lifetime.

An aspect of the present disclosure is directed to provide an organiclight emitting display device in which an electron transport layer isformed of materials which have different absolute values in the LUMOenergy level, and lifetime is enhanced by adjusting a content of thematerials.

Another aspect of the present disclosure is directed to provide anorganic light emitting display device in which an emission control layerand an electron transport layer with adjusted electron mobility areprovided, thereby enhancing lifetime.

Another aspect of the present disclosure is directed to provide anorganic light emitting display device in which lifetime is enhanced byadjusting an energy bandgap of an electron transport layer and an energybandgap of a charge generation layer adjacent to the electron transportlayer.

Another aspect of the present disclosure is directed to provide anorganic light emitting display device in which an energy bandgap of anelectron transport layer and an energy bandgap of a charge generationlayer adjacent to the electron transport layer are adjusted, and anemission control layer is provided, thereby enhancing lifetime.

The objects of the present disclosure are not limited to the aforesaid,but other objects not described herein will be clearly understood bythose skilled in the art from descriptions below.

Additional advantages and features of the disclosure will be set forthin part in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from practice of the disclosure. Theobjectives and other advantages of the disclosure may be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the disclosure, as embodied and broadly described herein, there isprovided an organic light emitting display device including an anode ona substrate, a first emission part that is disposed on the anode andincludes a first emission layer and a first electron transfer layer, asecond emission part that is disposed on the first emission part andincludes a second emission layer and a second electron transfer layer,and a cathode on the second emission part. At least one among the firstelectron transfer layer and the second electron transfer layer mayinclude a first material and a second material, and an absolute value ofa LUMO energy level of the first material may be larger than an absolutevalue of a LUMO energy level of the second material.

In another aspect of the present disclosure, there is provided anorganic light emitting display device including an anode on a substrate,a first emission part that is disposed on the anode and includes a firsthole transfer layer, a first emission layer, and a first electrontransfer layer, a second emission part that is disposed on the firstemission part and includes a second hole transfer layer, a secondemission layer, and a second electron transfer layer, and a cathode onthe second emission part. At least one among the first emission part andthe second emission part may include an emission control layer having anabsolute value of a highest occupied molecular orbital (HOMO) energylevel which is larger than an absolute value of a HOMO energy level ofthe first hole transfer layer or the second hole transfer layer.

Details of embodiments are included in a detailed description and thedrawings.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory and are intended to provide furtherexplanation of the disclosure as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate embodiments of the disclosure andtogether with the description serve to explain the principle of thedisclosure. In the drawings:

FIG. 1 is a diagram illustrating an organic light emitting displaydevice according to an embodiment of the present disclosure;

FIG. 2 is a diagram illustrating an organic light emitting deviceaccording to a first embodiment of the present disclosure;

FIG. 3A is a diagram showing an energy band diagram according to thefirst embodiment of the present disclosure;

FIG. 3B is a diagram showing an emission distribution with respect totime in an emission area according to the first embodiment of thepresent disclosure;

FIG. 4 is a diagram illustrating an organic light emitting deviceaccording to a second embodiment of the present disclosure;

FIG. 5 is a diagram showing lifetimes in a comparative example 1 (a1)and experiment examples 1 to 3 (A, B and C);

FIG. 6 is a diagram illustrating an organic light emitting deviceaccording to a third embodiment of the present disclosure;

FIG. 7 is a diagram showing an energy band diagram according to thethird embodiment of the present disclosure;

FIG. 8 is a diagram illustrating an organic light emitting deviceaccording to a fourth embodiment of the present disclosure;

FIG. 9 is a diagram showing lifetimes in experiment examples 4 to 7 (D,E, F and G) of the present disclosure;

FIG. 10A is a diagram showing an energy band diagram according to thesecond embodiment of the present disclosure and an energy band diagramaccording to the third embodiment of the present disclosure;

FIG. 10B is a diagram showing an emission distribution with respect totime in an emission area according to the second embodiment and thethird embodiment of the present disclosure;

FIG. 11 is a diagram illustrating an organic light emitting deviceaccording to a fifth embodiment of the present disclosure;

FIG. 12 is a diagram illustrating an organic light emitting deviceaccording to a sixth embodiment of the present disclosure;

FIG. 13 is a diagram showing an energy band diagram according to thesixth embodiment of the present disclosure;

FIG. 14 is a diagram illustrating an organic light emitting deviceaccording to a seventh embodiment of the present disclosure;

FIG. 15 is a diagram illustrating an organic light emitting deviceaccording to an eighth embodiment of the present disclosure;

FIG. 16 is a diagram showing lifetimes in a comparative example 2 (a2)and an experiment example 8 (H) of the present disclosure; and

FIG. 17 is a diagram showing lifetimes in a comparative example 2 (a2)and an experiment example 9 (I) of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Advantages and features of the present disclosure, and implementationmethods thereof will be clarified through following embodimentsdescribed with reference to the accompanying drawings. The presentdisclosure may, however, be embodied in different forms and should notbe construed as limited to the embodiments set forth herein. Rather,these embodiments are provided so that this disclosure will be thoroughand complete, and will fully convey the scope of the present disclosureto those skilled in the art. Further, the present disclosure is onlydefined by scopes of claims.

A shape, a size, a ratio, an angle, and a number disclosed in thedrawings for describing embodiments of the present disclosure are merelyan example, and thus, the present disclosure is not limited to theillustrated details. Like reference numerals refer to like elementsthroughout. In the following description, when the detailed descriptionof the relevant known function or configuration is determined tounnecessarily obscure the important point of the present disclosure, thedetailed description will be omitted. In a case where ‘comprise’,‘have’, and ‘include’ described in the present specification are used,another part may be added unless ‘only˜’ is used. The terms of asingular form may include plural forms unless referred to the contrary.

In construing an element, the element is construed as including an errorrange although there is no explicit description.

In describing a position relationship, for example, when a positionrelation between two parts is described as ‘on˜’, ‘over˜’, ‘under˜’, and‘next˜’, one or more other parts may be disposed between the two partsunless ‘just’ or ‘direct’ is used.

In describing a time relationship, for example, when the temporal orderis described as ‘after˜’, ‘subsequent˜’, ‘next˜’, and ‘before˜’, a casewhich is not continuous may be included unless ‘just’ or ‘direct’ isused.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, these elements shouldnot be limited by these terms. These terms are only used to distinguishone element from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of the present disclosure.

Features of various embodiments of the present disclosure may bepartially or overall coupled to or combined with each other, and may bevariously inter-operated with each other and driven technically as thoseskilled in the art can sufficiently understand. The embodiments of thepresent disclosure may be carried out independently from each other, ormay be carried out together in a co-dependent relationship.

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the accompanying drawings.

FIG. 1 is a diagram illustrating an organic light emitting displaydevice 1000 according to an embodiment of the present disclosure. Allthe components of the organic light emitting display device according toall embodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 1, the organic light emitting display device 1000 mayinclude a substrate 101, a thin film transistor (TFT) 700, and anorganic light emitting device D. The organic light emitting displaydevice 1000 may include a plurality of pixels P. A pixel P denotes anarea corresponding to a minimum unit where light is actually emitted,and may be referred to as a subpixel or a pixel area. Also, a certainplurality of pixels P may constitute a minimum group for realizing whitelight. For example, three subpixels may constitute one group, namely, ared subpixel, a green subpixel, and a blue subpixel may constitute onegroup. Alternatively, four subpixels may constitute one group, namely, ared subpixel, a green subpixel, a blue subpixel, and a white subpixelmay constitute one group. However, the present embodiment is not limitedthereto, and various pixel designs may be made. In FIG. 1, for theconvenience and brevity of description, only one pixel P is illustrated.

The TFT 700 may include a gate electrode 1115, a gate insulation layer1120, a semiconductor layer 1131, a source electrode 1133, and a drainelectrode 1135. The TFT 700 may be disposed on the substrate 101 and maysupply a signal to the organic light emitting device D. The TFT 700illustrated in FIG. 1 may be a driving TFT connected to a firstelectrode 102. A switching TFT or a capacitor for driving the organiclight emitting device D may be further disposed on the substrate 101.Also, in FIG. 1, the TFT 700 is illustrated as having an invertedstaggered structure, but may be formed in a coplanar structure.

The substrate 101 may be formed of an insulating material and/or amaterial having flexibility. The substrate 101 may be formed of glass,metal, plastic, and/or the like, but is not limited thereto. If anorganic light emitting display device is a flexible organic lightemitting display device, the substrate 101 may be formed of a flexiblematerial such as plastic and/or the like. Also, if an organic lightemitting device having flexibility is applied to a lighting device forvehicles or an automotive display device, various designs and a degreeof freedom of design of a lighting device for vehicles are securedaccording to a structure or an appearance of a vehicle.

The gate electrode 1115 may be formed on the substrate 101 and may beconnected to a gate line. The gate electrode 1115 may include amultilayer formed of one material among molybdenum (Mo), aluminum (Al),chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd),and copper (Cu) or an alloy thereof.

The gate insulation layer 1120 may be formed on the gate electrode 1115and may be formed of silicon oxide (SiOx), silicon nitride (SiNx), or amultilayer thereof, but is not limited thereto.

The semiconductor layer 1131 may be formed on the gate insulation layer1120, and may be formed of amorphous silicon (a-Si), polycrystallinesilicon (poly-Si), oxide semiconductor, or organic semiconductor. Whenthe semiconductor layer 1131 is formed of oxide semiconductor, thesemiconductor layer 1131 may be formed of indium tin oxide (ITO), indiumzinc oxide (IZO), zinc tin oxide (ZTO), indium gallium zinc oxide(IGZO), or indium tin zinc oxide (ITZO), but is not limited thereto.Also, an etch stopper may be formed on the semiconductor layer 1131 andmay protect the semiconductor layer 1131, but may be omitted dependingon a configuration of a device.

The source electrode 1133 and the drain electrode 1135 may be formed onthe semiconductor layer 1131. The source electrode 1133 and the drainelectrode 1135 may be formed of a single layer or a multilayer, and maybe formed of one material among molybdenum (Mo), aluminum (Al), chromium(Cr), gold (Au), titanium (Ti), nickel (Ni), neodymium (Nd), and copper(Cu) or an alloy thereof.

A planarization layer 1140 may be formed on the source electrode 1133and the drain electrode 1135 and may expose a portion of the drainelectrode 1135. The planarization layer 1140 may be formed of SiOx,SiNx, or a multilayer thereof. Alternatively, the planarization layer1140 may be formed of an acryl resin or a polyimide resin, but is notlimited thereto.

Moreover, a passivation layer may be further formed between theplanarization layer 140 and the TFT 700. The passivation layer may beformed of an inorganic material. The passivation layer protects the TFT700 and may expose a portion of the drain electrode 1135 similarly tothe planarization layer 1140.

The first electrode 102 may be formed on the planarization layer 1140.The first electrode 102 may be formed of indium tin oxide (ITO), indiumzinc oxide (IZO), or indium tin zinc oxide (ITZO) which is a transparentconductive material such as transparent conductive oxide (TCO), but isnot limited thereto. If the organic light emitting display device 1000is driven in a top emission type, the first electrode 102 may furtherinclude a reflector. Also, the first electrode 102 may be referred to asan anode or a pixel electrode.

The first electrode 102 may be electrically connected to the drainelectrode 1135 through a contact hole CH which is formed in a certainarea of the planarization layer 1140, and may be supplied with varioussignals through the TFT 700. In FIG. 1, the drain electrode 1135 isillustrated as being electrically connected to the first electrode 102,but the present embodiment is not limited thereto. As another example,the source electrode 1133 may be electrically connected to the firstelectrode 102 through the contact hole CH which is formed in the certainarea of the planarization layer 1140.

The organic light emitting display device 1000 of FIG. 1 may be the topemission type, and in this case, light emitted from an emission part1180 may be transferred in an up direction through the second electrode104. Also, when the organic light emitting display device 1000 is abottom emission type, the light emitted from an emission part 1180 maybe transferred in a down direction through the first electrode 102. Inthis case, the TFT 700 may be disposed in an area which does not overlapthe first electrode 102 or may be disposed in an area overlapping a banklayer 1170, so as not to obstruct a path of the light emitted from theemission part 1180.

A bank layer 1170 may be formed on the first electrode 102 and maydivide a pixel P. The bank layer 1170 may cover an end of the firstelectrode 102. Referring to FIG. 1, the bank layer 1170 may expose aportion of a top of the first electrode 102. The bank layer 1170 may beformed of an organic material such as a benzocyclobutene (BCB) resin, anacryl resin, a polyimide resin, and/or the like. The bank layer 1170 maybe formed of a photosensitive material having a black pigment. In thiscase, the bank layer 1170 may act as a light blocking member.

The organic light emitting device D may be formed at least partly on thebank layer 1170 and may include the first electrode 102, the emissionpart 1180, and the second electrode 104.

The second electrode 104 may be formed on the emission part 1180. Thesecond electrode 104 may be formed of gold (Au), silver (Ag), aluminum(Al), molybdenum (Mo), magnesium (Mg), lithium (Li), calcium (Ca),lithium fluoride (LiF), indium tin oxide (ITO), indium zinc oxide (IZO),indium tin zinc oxide (ITZO), and/or the like, may be formed of an alloythereof, or may be formed of a single layer or a multilayer. Examples ofthe alloy may include silver-magnesium (Ag;Mg), magnesium-lithiumfluoride (Mg;LiF), etc. However, the second electrode 104 is not limitedthereto. Also, the second electrode 104 may be referred to as a cathodeor a common electrode.

Moreover, an encapsulation part may be further formed on the secondelectrode 104. The encapsulation part prevents moisture from penetratinginto the emission part 1180. The encapsulation part may include aplurality of layers where different inorganic materials are stacked, orinclude a plurality of layers where an inorganic material and an organicmaterial are alternately stacked. Also, an encapsulation substrate maybe further formed on the encapsulation part. The encapsulation substratemay be formed of glass, plastic, or metal. The encapsulation substratemay be adhered to the encapsulation part by an adhesive.

FIG. 2 is a diagram illustrating an organic light emitting device 100according to a first embodiment of the present disclosure. The organiclight emitting device 100 in this embodiment or in any other embodimentof the present disclosure may correspond to the organic light emittingdevice D of FIG. 1.

The organic light emitting device 100 according to the first embodimentof the present disclosure illustrated in FIG. 2 may include a substrate101, first and second electrodes 102 and 104, and an emission part 1180between the first and second electrodes 102 and 104. The emission part1180 may include a first emission part 110 and a second emission part120.

The emission part 1180 illustrated in FIG. 2 may have a common emissionlayer structure and may emit white light. The emission part 1180 havingthe common emission layer structure may be formed by using a common maskwhere all pixels are opened, and may be stacked in the same structure inall pixels without patterns by pixel. That is, the emission part 1180having the common emission layer structure may have a connection orextend from one pixel to an adjacent pixel without being broken orinterrupted and may share a plurality of pixels.

The substrate 101 may be formed of an insulating material and/or amaterial having flexibility. The substrate 101 may be formed of glass,metal, plastic, and/or the like, but is not limited thereto.

The first electrode 102 is an anode that supplies a hole, and may beformed of a transparent conductive material having a high work function.Here, examples of the transparent conductive material may include ITO,IZO, ITZO, etc.

The second electrode 104 is a cathode that supplies an electron, and maybe formed of a metal material having a relatively low work function.Examples of the metal material may include silver (Ag), titanium (Ti),aluminum (Al), molybdenum (Mo), etc.

Moreover, a capping layer may be further formed on the second electrode104, for protecting the organic light emitting device. Also, the cappinglayer may be omitted depending on the structure or characteristic of theorganic light emitting device.

The first emission part 110, which includes a first hole transport layer(HTL) 112, a first emission layer (EML) 114, and a first electrontransport layer (ETL) 116, may be formed on the first electrode 102.

A hole supplied through the first HTL 112 and an electron suppliedthrough the first ETL 116 may be recombined in the first EML 114 togenerate an exciton. An area where the exciton is generated in the firstEML 114 may be referred to as a recombination area (a recombinationzone) or an emission area (an emission zone).

Moreover, the second emission part 120 which includes a second HTL 122,a second EML 124, and a second ETL 126 may be formed on the firstemission part 110.

A hole supplied through the second HTL 122 and an electron suppliedthrough the second ETL 126 may be recombined in the second EML 124 togenerate an exciton. An area where the exciton is generated in thesecond EML 124 may be referred to as a recombination area (arecombination zone) or an emission area (an emission zone).

Moreover, a charge generation layer (CGL) 140 may be formed between thefirst emission part 110 and the second emission part 120. The CGL 140may adjust a charge balance between the first emission part 110 and thesecond emission part 120 and may include an N-type CGL and a P-type CGL.

The first EML 114 and the second EML 124 may be emission layers thatemit light of different colors. For example, the first EML 114 may beone among a red EML, a green EML, and a blue EML, and the second EML 124may be an emission layer having a color that differs from that of thefirst EML 114.

In order to smoothly transfer electrons to the first EML 114 and thesecond EML 124, the first ETL 116 and the second ETL 126 may each beformed of a material which has high electron mobility. In this case,since the electrons are quickly transferred to the first EML 114 and thesecond EML 124, a driving voltage does not increase, but it is difficultto adjust a balance of electrons and holes in the first EML 114 and thesecond EML 124. Also, there is a problem where as time elapses, lifetimeis reduced. Details where lifetime is reduced as time elapses will bedescribed with reference to FIGS. 3A and 3B.

FIG. 3A is a diagram showing an energy band diagram according to thefirst embodiment of the present disclosure.

As shown in FIG. 3A, an electron (e-) supplied through the first ETL 116and a hole (h+) supplied through the first HTL 112 may be recombined inthe first EML 114 to generate an exciton. A combination area where anelectron and a hole are combined in the first EML 114 may be referred toas an emission area (an emission zone) or a recombination area (arecombination zone). In FIG. 3A, an arrow indicates the direction of anincreasing lifetime.

The first ETL 116 may be formed of a material, which has high electronmobility, for smoothly transferring an electron to the first EML 114 andlowering the driving voltage, and thus, as shown in FIG. 3A, an emissionarea of the first EML 114 may be disposed closer to a center of thefirst EML 114 than to the first HTL 112 (referred to by {circle around(1)}). Also, it can be seen that a non-emission area A appears as timeelapses (referred to by {circle around (2)}). Furthermore, it can beseen that when time further elapses, the non-emission area A is enlargedin comparison with {circle around (2)} (referred to by {circle around(3)}). Since the non-emission area A cannot emit light, the non-emissionarea A cannot contribute to emission of light from the first EML 114.Therefore, it can be seen that as time elapses, the emission area isformed in or shifted to an interface between the first HTL 112 and thefirst EML 114, and thus, the non-emission area A incapable ofcontributing to emission of light from the first EML 114 is enlarged.Also, it can be seen that as time elapses, the emission area moves fromthe first EML 114 to the interface between the first HTL 112 and thefirst EML 114. That is, as time elapses, an emission position changes,and thus, lifetime is reduced.

FIG. 3B is a diagram showing an emission distribution with respect totime in an emission area according to the first embodiment of thepresent disclosure.

As illustrated in FIG. 3B, it can be seen that as time elapses (referredto by an arrow), a non-emission area A is enlarged, and thus, anemission distribution is narrowed. Therefore, as time elapses, lifetimeis reduced.

As described above with reference to FIGS. 3A and 3B, as time elapses,an emission position changes, a non-emission area is enlarged, and anemission distribution is narrowed, causing a reduction in lifetime.Therefore, the inventor has recognized that a position of an emissionarea and an emission distribution with respect to time should beimproved for enhancing a lifetime of an organic light emitting displaydevice.

Therefore, embodiments of the present disclosure provide an organiclight emitting display device in which an electron and a hole arerecombined in an EML by adjusting a balance of electrons and holes, andan emission area has a broad emission distribution even when an emissionposition moves as time elapses, thereby enhancing lifetime.

This will be described with reference to FIG. 4.

FIG. 4 is a diagram illustrating an organic light emitting device 200according to a second embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

The organic light emitting device 200 according to the second embodimentof the present disclosure illustrated in FIG. 4 may include a substrate201, first and second electrodes 202 and 204, and an emission part 1180between the first and second electrodes 202 and 204. The emission part1180 may include a first emission part 210 and a second emission part220.

The emission part 1180 illustrated in FIG. 4 may have a common emissionlayer structure and may emit white light. The emission part 1180 havingthe common emission layer structure may be formed by using a common maskwhere all pixels are opened, and may be stacked in the same structure inall pixels without being patterned for each pixel. That is, the emissionpart 1180 having the common emission layer structure may have aconnection or extend from one pixel to an adjacent pixel without beingbroken or interrupted and may share a plurality of pixels.

Also, light emitted from a plurality of emission layers 214 and 224included in the emission part 1180 may be combined to emit white lightthrough the first electrode 202 or the second electrode 204.Alternatively, the emission part 1180 may have a patterned emissionlayer structure. The emission part 1180 having the patterned emissionlayer structure may have a structure where a plurality of emissionlayers (for example, a red (R) emission layer, a green (G) emissionlayer, and a blue (B) emission layer) which respectively emit lighthaving different colors are divisionally provided in a plurality ofpixels, respectively, and each of the plurality of pixels may emit lighthaving a monocolor. Also, a patterned emission layer may include amonocolor. Each of the plurality of emission layers may bepattern-deposited in a corresponding pixel by using an opened mask (forexample, a fine metal mask (FMM)). Therefore, the first EML 214 and thesecond EML 224 are illustrated in FIG. 4. However, each of the first EML214 and the second EML 224 may be configured as a red EML, a green EML,and a blue EML disposed in each of the plurality of pixels.

The substrate 201 may be formed of an insulating material and/or amaterial having flexibility. The substrate 201 may be formed of glass,metal, plastic, and/or the like, but is not limited thereto. If anorganic light emitting display device is a flexible organic lightemitting display device, the substrate 201 may be formed of a flexiblematerial such as plastic and/or the like. Also, if an organic lightemitting device having flexibility is applied to a lighting device forvehicles, various designs and a degree of freedom of design of a lightdevice for vehicles are secured according to a structure or anappearance of a vehicle.

The first electrode 202 is an anode that supplies a hole, and may beformed of indium tin oxide (ITO), indium zinc oxide (IZO), or the likewhich is a transparent conductive material such as transparentconductive oxide (TCO). Alternatively, the first electrode 202 may beformed of gold (Au), silver (Ag), aluminum (Al), molybdenum (Mo),magnesium (Mg), lithium (Li), calcium (Ca), lithium fluoride (LiF), ITO,IZO, ITZO, and/or the like, may be formed of an alloy thereof, or may beformed of a single layer or a multilayer. Examples of the alloy mayinclude Ag:Mg, Mg:LiF, etc. However, a material of the first electrode202 is not limited thereto.

Moreover, the first electrode 202 may include a reflective layer inorder that light emitted from each of the EMLs 214 and 224 is notirradiated in a down direction through the first electrode 202. Indetail, the first electrode 202 may have a three-layer structure where afirst transparent layer, a reflective layer, and a second transparentlayer are sequentially stacked. For example, the first transparent layerand the second transparent layer may each be formed of transparentconductive oxide (TCO) such as ITO, IZO, ITZO, or the like. Thereflective layer between the two transparent layers may be formed of ametal material such as copper (Cu), silver (Ag), palladium (Pd), an Agalloy, or the like. For example, the first electrode 202 may be formedof ITO/Ag/ITO or Ag/Pd/Cu. Alternatively, the first electrode 202 mayhave a two-layer structure where a transparent layer and a reflectivelayer are stacked.

The second electrode 204 is a cathode that supplies an electron, and maybe formed of gold (Au), silver (Ag), aluminum (Al), Mo, magnesium (Mg),lithium (Li), calcium (Ca), lithium fluoride (LiF), indium tin oxide(ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO) and/or thelike, or may be formed of an alloy thereof. Alternatively, the secondelectrode 204 may be formed of a single layer or a multilayer. Examplesof the alloy may include silver-magnesium (Ag:Mg), magnesium-lithiumfluoride (Mg:LiF), etc. However, a material of the second electrode 204is not limited thereto.

The first electrode 202 and the second electrode 204 may be referred toas an anode and a cathode, respectively. That is, the emission part 1180may be provided between the anode and the cathode. Also, the firstelectrode 202 and the second electrode 204 may be referred to as a pixelelectrode and a common electrode, respectively. Alternatively, the firstelectrode 202 may be formed as a transmissive electrode, and the secondelectrode 204 may be formed as a semitransmissive electrode.Alternatively, the first electrode 202 may be formed as a reflectiveelectrode, and the second electrode 204 may be formed as asemitransmissive electrode. Alternatively, the first electrode 202 maybe formed as a semitransmissive electrode, and the second electrode 204may be formed as a transmissive electrode. Alternatively, at least oneamong the first and second electrodes 202 and 204 may be formed as asemitransmissive electrode.

Moreover, a capping layer may be further formed on the second electrode204, for protecting the organic light emitting device. Also, the cappinglayer may be omitted depending on the structure or characteristic of theorganic light emitting device.

The first emission part 210 which includes a first HTL 212, a first EML214, and a first ETL 216 may be disposed on the first electrode 202.

A hole supplied through the first HTL 212 and an electron suppliedthrough the first ETL 216 may be recombined in the first EML 214 togenerate an exciton. An area where the exciton is generated in the firstEML 214 may be referred to as a recombination area (a recombinationzone) or an emission area (an emission zone).

The first HTL 212 may be formed of one or more ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-benzidine (NPB), andN,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine (TPD), but is notlimited thereto.

Moreover, a hole injection layer (HIL) may be further formed on thefirst electrode 202. The HIL may smoothly transfer a hole, supplied fromthe first electrode 202, to the first HTL 212. The HIL enables the holeto be smoothly injected. The HIL may be formed of one or more ofdipyrazino[2,3-f:2′,3′-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile(HAT-CN), cupper phthalocyanine (CuPc), poly(3,4)-ethylenedioxythiophene(PEDOT), N,N′-bis(naphthalen-1-yl)-N,N-bis(phenyl)2-2′-dimethylbenzidine(α-NPD), N,N″-bis(3-methylphenyl)-N,N″-bis(phenyl)-benzidine (TPD),N,N′-bis(naphthalene-1-yl)-N,N′bis(phenyl)-benzidine (NPB),4,4′,4″-tris(carbazol-9-yl)triphenylamine (TcTa),2,2″,7,7″-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (spiro-TAD),and 4,4′-bis(carbazol-9-yl)biphenyl (CBP), but is not limited thereto.

The HIL may be formed by doping a P-type dopant on a materialconstituting the first HTL 212. In this case, the HIL and the first HTL212 may be formed through a continuous process using one processequipment. The P-type dopant may be formed of2,3,5,6-tetrafluoro-7,7,8,8-tetracyanl-quinodimethane (F4-TCNQ) and/orthe like, but is not limited thereto.

Moreover, the second emission part 220 which includes a second HTL 222,a second EML 224, and a second ETL 226 may be formed on the firstemission part 210.

A hole supplied through the second HTL 222 and an electron suppliedthrough the second ETL 226 may be recombined in the second EML 224 togenerate an exciton. An area where the exciton is generated in thesecond EML 224 may be referred to as a recombination area (arecombination zone) or an emission area (an emission zone).

Moreover, the second HTL 222 may be formed of a material which is thesame as that of the first HTL 212, but is not limited thereto.

Moreover, an electron injection layer (EIL) may be further formed on thesecond ETL 226, e.g. between the second electrode 204 and the second ETL226. The EIL may smoothly transfer an electron, supplied from the secondelectrode 204, to the second ETL 226.

The first HTL 212, the second HTL 222, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 214 and thesecond EML 224. Also, the first ETL 216, the second ETL 226, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 214 and the second EML 224.

Moreover, a charge generation layer (CGL) 240 may be formed between thefirst emission part 210 and the second emission part 220. The CGL 240may adjust a charge balance between the first emission part 210 and thesecond emission part 220 and may include an N-type CGL and/or a P-typeCGL. The N-type CGL may inject an electron into the first EML 214 andmay be formed of an organic layer doped with metal and/or the like, butis not limited thereto. The P-type CGL may inject a hole into the secondEML 224. The P-type CGL may be formed of an organic layer including aP-type dopant, but is not limited thereto.

The first EML 214 and the second EML 224 may be EMLs that emit light ofdifferent colors. For example, the first EML 214 may be one among a redEML, a green EML, and a blue EML, and the second EML 224 may be an EMLhaving a color that differs from that of the first EML 214. Therefore,the organic light emitting device according to an embodiment of thepresent disclosure may be a light emitting device that emits white lightfrom each of the first EML 214 and the second EML 224. Alternatively,the first EML 214 and the second EML 224 may be EMLs that emit light ofthe same color. For example, each of the first EML 214 and the secondEML 224 may be one among a red EML, a green EML, and a blue EML.Therefore, the organic light emitting device according to an embodimentof the present disclosure may be a monocolor light emitting device thatemits light of the same color.

Moreover, the first EML 214 and the second EML 224 may each include atleast one host and at least one dopant. The at least one host may be ahost having a hole characteristic or a host having an electroncharacteristic. Alternatively, the at least one host may be a mixed hostincluding two or more kinds of hosts. If the at least one host includestwo or more kinds of hosts, the at least one host may include a hosthaving a hole characteristic and a host having an electroncharacteristic. Also, the at least one dopant may include a fluorescentdopant or a phosphorescent dopant.

If each of the first EML 214 and the second EML 224 is the red EML, ahost constituting the red EML may include one or more host materials,and examples of the host materials may include4,4′-bis(carbozol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene(MCP),N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), Be complex, etc. A dopant constituting the red EML may include aphosphorescent dopant, and examples of the phosphorescent dopant mayincludebis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate)iridium(III)(Ir(btp)₂(acac)), bis(1-phenylisoquinoline)(acetylacetonate)iridium(III)(Ir(piq)₂(acac)), tris(1-phenylquinoline)iridium(III) (Ir(piq)₃),5,10,15,20-tetraphenyltetrabenzoporphyrin platinum complex (Pt(TPBP)),etc. Also, the dopant constituting the red EML may be a fluorescentdopant, and examples of the fluorescent dopant may include perylene,etc. The materials of the host or the dopant constituting the red EML donot limit details of the present disclosure.

If each of the first EML 214 and the second EML 224 is the green EML, ahost constituting the green EML may include one or more host materials,and examples of the host materials may include4,4′-bis(carbozol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yObenzene(MCP),N,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine(NPD), Be complex, anthracene derivatives, etc. A dopant constitutingthe green EML may be a phosphorescent dopant, and examples of thephosphorescent dopant may include tris(2-phenylpyridine)iridium(III)(Ir(ppy)₃), Bis(2-phenylpyridine)(acetylacetonate)iridium(III)(Ir(ppy)₂(acac)), etc. Also, the dopant constituting the green EML maybe a fluorescent dopant, and examples of the fluorescent dopant mayinclude tris(8-hydroxy-quinolinato)aluminum (Alq₃), etc. The materialsof the host or the dopant constituting the green EML do not limitdetails of the present disclosure.

If each of the first EML 214 and the second EML 224 is the blue EML, ahost constituting the blue EML may include one or more host materials,and examples of the host materials may include4,4′-bis(carbozol-9-yl)biphenyl (CBP), 1,3-bis(carbazol-9-yl)benzene(MCP), 9,10-di(naphth-2-yl)anthracene (ADN), anthracene derivatives,etc. A dopant constituting the blue EML may be a phosphorescent dopant,and examples of the phosphorescent dopant may includebis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium(III)(FIrpic), etc. Also, the dopant constituting the blue EML may be afluorescent dopant, and examples of the fluorescent dopant may includepolyfluorene (PFO)-based polymer, polyphenylenevinylene (PPV)-basedpolymer, pyrene derivatives, etc. The materials of the host or thedopant constituting the blue EML do not limit details of the presentdisclosure.

In the second embodiment of the present disclosure, a balance of holesand electrons in the second EML 224 is maintained by adjusting anelectron mobility of the second ETL 226, there providing an organiclight emitting display device with enhanced lifetime. Therefore, thesecond ETL 226 is formed of at least two materials which have differentabsolute values in a lowest unoccupied molecular orbital (LUMO) energylevel, and under this condition, the inventors have done an experimentfor checking whether lifetime is affected by a content of the at leasttwo materials.

This will be described below with reference to the following Table 1 andFIG. 5.

TABLE 1 Driving Efficiency Voltage (V) (cd/A) CIEx CIEy Comparative 7.512.1 0.135 0.068 Example 1 Experiment 7.7 10.0 0.135 0.068 Example 1Experiment 7.7 12.2 0.135 0.068 Example 2 Experiment 7.9 11.8 0.1350.068 Example 3

In Table 1, the comparative example 1 and the experiment examples 1 to 3have been experimented by applying the organic light emitting device ofFIG. 4. In the comparative example 1 and the experiment examples 1 to 3,one pixel includes a red subpixel, a green subpixel, and a bluesubpixel.

In the comparative example 1, the first electrode 202 is formed on thesubstrate 201, the first HTL 212 is formed ofN,N′-bis(naphthalene-1-yl)-N,N′-bis(phenyl)-2,2′-dimethylbenzidine (NPD)and/or the like, and in an area adjacent to the substrate 201, the HILis formed by doping2,3,5,6-tetrofluoro-7,7,8,8-tetracyano-quinodimethane (F4-TCNQ) and/orthe like.

Moreover, in a red subpixel area, the first EML 214 is formed by dopingbis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate)iridium(III)(Ir(btp)₂(acac)) as a dopant on Be complex which is a red host. Also, ina green subpixel area, the first EML 214 is formed by dopingBis(2-phenylpyridine)(acetylacetonate)iridium(III) (Ir(ppy)₂(acac)) as adopant on anthracene derivatives and 4,4′-bis(carbozol-9-yl)biphenyl(CBP) which are green hosts. Also, in a blue subpixel area, the firstEML 214 is formed by doping pyrene derivatives as dopants on anthracenederivatives which are blue hosts.

Moreover, the first ETL 216 is formed in a whole portion of each of thered subpixel area, the green subpixel area, and the blue subpixel area.For example, the first ETL 216 may be formed one oftris(8-hydroxy-quinolinato)aluminum (Alq₃) and3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ).

The N-type CGL 240 is formed by doping a dopant such as metal or thelike on hosts that are anthracene derivatives. Also, the second HTL 222is formed of NPD in a whole portion of each of the red subpixel area,the green subpixel area, and the blue subpixel area, and a P-type CGL isformed in an interface between the second HTL 222 and the N-type CGL bydoping F4-TCNQ on NPD.

Moreover, in the red subpixel area, the second EML 224 is formed bydopingbis(2-benzo[b]thiophen-2-yl-pyridine)(acetylacetonate)iridium(III)(Ir(btp)₂(acac)) as a dopant on Be complex which is a red host. Also, inthe green subpixel area, the second EML 224 is formed by dopingBis(2-phenylpyridine)(acetylacetonate)iridium(III) (Ir(ppy)₂(acac)) as adopant on anthracene derivatives and 4,4′-bis(carbozol-9-yl)biphenyl(CBP) which are green hosts. Also, in the blue subpixel area, the secondEML 224 is formed by doping pyren derivatives as dopants on anthracenederivatives which are blue hosts.

Moreover, by co-depositing Alq₃ and Liq at a ratio of 1:1, the secondETL 226 and the second electrode 204 are formed in a whole portion ofeach of the red subpixel area, the green subpixel area, and the bluesubpixel area. Here, a first material of the second ETL 226 includes amaterial which is less in absolute value of a LUMO energy level than8-hydroxyquinolinolato-lithium (Liq) which is a second material. Thatis, a first material of the second ETL 226 is one among materials havingan absolute value of a LUMO energy level which is within a range of 2.40eV to 2.60 eV, and for example, may be one amongtris(8-hydroxy-quinolinato)aluminum (Alq₃) and3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ). Also, anabsolute value of a LUMO energy level of Liq which is a second materialis within a range of 2.60 eV to 2.90 eV.

Moreover, a capping layer is formed of NPD. Herein, the above-describedmaterials of the organic layers do not limit details of the presentdisclosure.

The experiment examples 1 to 3 are configured identically to thecomparative example 1. The second ETL 226 is formed of at least twomaterials (for example, a first material and a second material). In thiscase, an absolute value of a LUMO energy level of the first material isgreater than an absolute value of a LUMO energy level of the secondmaterial, and the second ETL 226 is formed by co-depositing the firstmaterial and the second material. In the at least two materials, theabsolute value of the LUMO energy level of the first material has arange of 2.91 eV to 3.40 eV, and the absolute value of the LUMO energylevel of the second material may have a range of 2.60 eV to 2.90 eV.Also, the first material includes one among anthracene derivatives,triazine derivatives, and carbozole derivatives, and the second materialincludes 8-hydroxyquinolinolato-lithium (Liq). Also, in the experimentexamples 1 to 3, a ratio of the first material to the second material isdifferently configured. That is, a ratio of the first material to thesecond material is 2:1 in the experiment example 1, a ratio of the firstmaterial to the second material is 1:1 in the experiment example 2, anda ratio of the first material to the second material is 1:2 in theexperiment example 3. Such a ratio corresponds to a value which is setfor experiment. A ratio being 1:2 in the experiment example 3 denotesthat a content of the second material is higher than that of the firstmaterial, and for example, may denote that when a sum of a weight of thefirst material and a weight of the second material is 100 wt %, acontent of the second material exceeds 50 wt %. Also, a ratio being 1:1in the experiment example 2 denotes that a content of the first materialis equal to that of the second material.

In Table 1, color coordinates (CIEx, CIEy) represent blue colorcoordinates (0.135, 0.068). Table 1 shows a result that is obtained bycomparing the driving voltages (V) and the efficiencies (cd/A) withrespect to a current density of 5 mA/cm² in a state where the blue colorcoordinates are identically set.

To describe the driving voltages (V), as shown in Table 1, it can beseen that in the driving voltages (V), the experiment examples 1 to 3increase a little in comparison with the comparative example 1. Also, itcan be seen that the driving voltage of the experiment example 3increases a little in comparison with the experiment examples 1 and 2.

To describe the efficiencies (cd/A), it can be seen that the comparativeexample 1, the experiment example 2, and the experiment example 3 arealmost similar. Also, it can be seen that the experiment example 2 andthe experiment example 3 increase further in efficiency than theexperiment example 1. That is, it can be seen that efficiency furtherincreases in the experiment examples 2 and 3, where a content of thesecond material is equal to or higher than that of the first material,than the experiment example 1 where a content of the second material islower than that of the first material.

Lifetime will be described below with reference to FIG. 5. A lifetimemeasurement result shown in FIG. 5 has been obtained through measurementfor an experiment, and a measured lifetime does not limit details of thepresent disclosure. Therefore, FIG. 5 shows a result obtained measuringlifetime for checking whether the lifetime is enhanced under conditionsof the comparative example 1 and the experiment examples 1 to 3.

FIG. 5 is a diagram showing lifetimes in the comparative example 1 andexperiment examples 1 to 3.

In FIG. 5, the abscissa axis indicates time (hr), and the ordinate axisindicates a luminance drop rate (%). Also, the comparative example 1 isreferred to as a1, the experiment example 1 is referred to as A, theexperiment example 2 is referred to as B, and the experiment example 3is referred to as C.

As shown in FIG. 5, when initial emission luminance is 100%, it can beseen that in time (i.e., a 95% lifetime (T95) of the organic lightemitting device) taken until luminance is reduced by 95%, thecomparative example 1 is about 210 hours, the experiment examples 1 and2 are about 280 hours, and the experiment example 3 is about 460 hours.Therefore, it can be seen that the lifetime of the experiment example 3increases by about 2.1 times lifetime of the comparative example 1. Thatis, it can be seen that the lifetime is further enhanced in theexperiment example 3, where a content of the second material is higherthan that of the first material, than the comparative example 1 and theexperiment examples 1 and 2.

Moreover, FIG. 5 shows blue lifetime, and a total lifetime of theorganic light emitting display device is enhanced further in theexperiment example 3 than the comparative example 1 and the experimentexamples 1 and 2.

Through such an experiment result, it can be seen that in efficiency,the comparative example 1 is almost similar to the experiment examples 1to 3 of the present disclosure. Also, since electron mobility is lowereddue to the second material having an absolute value of a LUMO energylevel which is greater than an absolute value of a LUMO energy level ofthe first material, it can be seen that the experiment examples 1 to 3of the present disclosure increases a little more in driving voltagethan the comparative example 1.

Moreover, efficiency and a driving voltage based on a content of thefirst material and the second material included in the ETL in theexperiment examples 1 to 3 of the present disclosure will be describedbelow. It can be seen that the experiment examples 2 and 3 where acontent of the second material is equal to or higher than that of thefirst material increases further in efficiency than the experimentexample 1 where a content of the second material is lower than that ofthe first material. It can be seen that the experiment example 3 where acontent of the second material is higher than that of the first materialincreases a little more in driving voltage than the experiment examples1 and 2 where a content of the second material is equal to or lower thanthat of the first material. Also, it can be seen that the experimentexample 3 where a content of the second material is higher than that ofthe first material is enhanced further in lifetime than the experimentexamples 1 and 2 where a content of the second material is equal to orlower than that of the first material. Therefore, it can be seen thatthe driving voltage increases a little more, efficiency is reduced alittle more, and lifetime is further enhanced in a case, where a contentof the second material is higher than that of the first material, than acase where a content of the second material is equal to or lower thanthat of the first material. Accordingly, it can be seen that lifetime isfurther enhanced when an ETL is formed of two materials having differentabsolute values of LUMO energy levels, and a material having arelatively smaller absolute value of a LUMO energy level among the twomaterials is higher in content than a material having a relativelylarger absolute value of a LUMO energy level.

Therefore, the ETL according to an embodiment of the present disclosureis formed of two materials having different absolute values of LUMOenergy levels, and by adjusting a content of the two materials, the ETLis configured in order to reduce electron mobility. That is, an absolutevalue of a LUMO energy level of a first material of two differentmaterials is adjusted higher than an absolute value of a LUMO energylevel of a second material, and thus, an electron is easily injectedinto an EML. The absolute value of the LUMO energy level of the firstmaterial may have a range of 2.91 eV to 3.40 eV, and the absolute valueof the LUMO energy level of the second material may have a range of 2.60eV to 2.90 eV. Also, the first material is one among materials having anabsolute value of a LUMO energy level which is within a range of 2.91 eVto 3.40 eV. For example, the first material may be one among anthracenederivatives, triazine derivatives, and carbozole derivatives, but is notlimited thereto. The second material is one among materials having anabsolute value of a LUMO energy level which is within a range of 2.60 eVto 2.90 eV, and for example, may include 8-hydroxyquinolinolato-lithium(Liq). Also, the first material and the second material are mixedthrough co-deposition.

Moreover, a content of the second material is adjusted higher than thatof the first material, or the second material having the absolute valueof the LUMO energy level is less than the absolute value of the LUMOenergy level of the first material is configured higher in content thanthe first material, and thus, an electron mobility of an ETL is lowered,whereby an emission area where a balance of electrons and holes isformed is located in an EML. Therefore, a lifetime of the EML isenhanced. That is, since, the second material, e.g. Liq, is configuredhigher in content than the first material, electron mobility is lowered,and thus, the emission area where a balance of electrons and holes isformed is located in the EML, thereby enhancing lifetime. Also, acontent of the second material exceeds 50 wt % in the ETL. Also, the ETLmay have a thickness of about 10 nm to 40 nm. When a thickness of theETL is less than about 10 nm, the ETL cannot act as an ETL, and when athickness of the ETL is more than about 40 nm, a thickness of theorganic light emitting device is increased, causing an increase in thedriving voltage or a reduction in efficiency or lifetime.

Moreover, the first ETL 216 may each be formed of the first material andthe second material of the second ETL 226. For example, the first ETL216 may be formed of one of tris(8-hydroxy-quinolinato)aluminum (Alq₃),3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ),8-hydroxyquinolinolato-lithium (Liq), anthracene derivatives, triazinederivatives, and carbozole derivatives, but are not limited thereto.

Moreover, in the second embodiment of the present disclosure, the secondETL 226 has been described as an example, but the above-describeddetails may be applied to the first ETL 216. Even in this case, lifetimeis enhanced. Alternatively, the above-described details may be appliedto all of the first and second ETLs 216 and 226, and even in this case,lifetime is enhanced. Therefore, at least one among the first and secondETLs 216 and 226 may be formed of two materials having differentabsolute values of LUMO energy levels, and an ETL formed by adjusting acontent of the two materials may be applied as the first and second ETLs216 and 226. Also, in the present embodiment, the organic light emittingdevice including two emission parts has been described as an example,but the above-described details may be applied to an organic lightemitting device including three or more emission parts. Even in thiscase, the ETL according to the present embodiment may be applied.

In the second embodiment of the present disclosure, it can be seen thatin the ETL, as described above, the second material having the absolutevalue of the LUMO energy level which is less than the absolute value ofthe LUMO energy level of the first material is configured higher incontent than the first material, and thus, lifetime is enhanced. Also,the inventor proposes an organic light emitting device in which lifetimeis not reduced despite the elapse of time, namely, despite the elapse ofa long time.

FIG. 6 is a diagram illustrating an organic light emitting device 300according to a third embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 6, the organic light emitting device 300 according tothe third embodiment of the present disclosure may include an emissionpart 1180 between a first electrode 302 and a second electrode 304. Theemission part 1180 may include a first emission part 310 and a secondemission part 320. A substrate 301, the first electrode 302, the firstemission part 310, the emission part 1180, and the second electrode 304illustrated in FIG. 6 may be substantially the same as the substrate201, the first electrode 202, the first emission part 210, the emissionpart 1180, and the second electrode 204 described above with referenceto FIG. 4. Thus, detailed descriptions of the substrate 301, the firstelectrode 302, the first emission part 310, the emission part 1180, andthe second electrode 304 illustrated in FIG. 6 are not provided.

The first emission part 310 may include a first HTL 312, a first EML314, and a first ETL 316 which are disposed on the first electrode 302.A hole supplied through the first HTL 312 and an electron suppliedthrough the first ETL 316 may be recombined in the first EML 314 togenerate an exciton. An area where the exciton is generated in the firstEML 314 may be referred to as a recombination area (a recombinationzone) or an emission area (an emission zone).

Moreover, an HIL may be further formed on the first electrode 302. TheHIL may smoothly transfer a hole, supplied from the first electrode 302,to the first HTL 312. Also, the first HTL 312 may be a P-type HTL dopedwith a P-type dopant.

Moreover, the second emission part 320 which includes a second HTL 322,a second EML 324, an emission control layer (ECL) 323, and a second ETL326 may be formed on the first emission part 310.

A hole supplied through the second HTL 322 and the ECL 323 and anelectron supplied through the second ETL 326 may be recombined in thesecond EML 324 to generate an exciton. An area where the exciton isgenerated in the second EML 324 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an EIL may be further formed on the second ETL 326. The EILmay smoothly transfer an electron supplied from the second electrode 304to the second ETL 326.

The first HTL 312, the second HTL 322, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 314 and thesecond EML 324. Also, the first ETL 316, the second ETL 326, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 314 and the second EML 324.

The second ETL 326 may be formed of two materials having differentabsolute values of LUMO energy levels, and by adjusting a content of thetwo materials, the second ETL 326 may be configured in order to reduceelectron mobility. That is, an absolute value of a LUMO energy level ofa first material of two different materials is adjusted higher than anabsolute value of a LUMO energy level of a second material, and thus, anelectron is easily injected into the second EML 324. The absolute valueof the LUMO energy level of the first material may have a range of 2.91eV to 3.40 eV, and the absolute value of the LUMO energy level of thesecond material may have a range of 2.60 eV to 2.90 eV. Also, the firstmaterial is one among materials having an absolute value of a LUMOenergy level which is within a range of 2.91 eV to 3.40 eV. For example,the first material may be one of anthracene derivatives, triazinederivatives, and carbozole derivatives, but is not limited thereto. Thesecond material is one among materials having an absolute value of aLUMO energy level which is within a range of 2.60 eV to 2.90 eV, and forexample, may include 8-hydroxyquinolinolato-lithium (Liq). Also, thefirst material and the second material may be mixed throughco-deposition.

Moreover, a content of the second material is adjusted higher than thatof the first material, or the second material having the absolute valueof the LUMO energy level which is less than the absolute value of theLUMO energy level of the first material is configured higher in contentthan the first material, and thus, an electron mobility of an ETL islowered, whereby an emission area where a balance of electrons and holesis formed is located in an EML. Therefore, lifetime of the second EML324 is enhanced. That is, since Liq which is the second material isconfigured higher in content than the first material, electron mobilityis lowered, and thus, the emission area where a balance of electrons andholes is formed is located in the second EML 324, thereby enhancinglifetime. Also, a content of the second material exceeds 50 wt % in thesecond ETL 326. Also, the second ETL 326 may have a thickness of about10 nm to 40 nm. When a thickness of the second ETL 326 is less thanabout 10 nm, the second ETL 326 cannot act as an ETL, and when athickness of the second ETL 326 is more than about 40 nm, a thickness ofthe organic light emitting device is increased, causing an increase inthe driving voltage or a reduction in efficiency or lifetime.

Moreover, the first ETL 316 may each be formed of the first material andthe second material of the second ETL 326. For example, the first ETL316 may be formed of one of tris(8-hydroxy-quinolinato)aluminum (Alq₃),3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ),8-hydroxyquinolinolato-lithium (Liq), anthracene derivatives, triazinederivatives, and carbozole derivatives, but are not limited thereto.

The ECL 323 may be formed of two materials which have different absolutevalues in LUMO energy level, and may be provided in an emission partincluding the second ETL 326 formed of two materials. Therefore,provided is an organic light emitting display device in which a balanceof electrons and holes is adjusted in the second EML 324, lifetime isstably reduced as time elapses, and lifetime is long. That is, if thesecond ETL 326 and the ECL 323 are all provided, lifetime is furtherenhanced, and lifetime linearly changes without being changed to a bellshape as time elapses, thereby providing an organic light emittingdisplay device having long lifetime.

The ECL 323 may be provided between the second HTL 322 and the secondEML 324. An absolute value of an highest occupied molecular orbitals(HOMO) energy level of the ECL 323 may be adjusted greater than anabsolute value of an HOMO energy level of the second HTL 322, and thus,the ECL 323 may act as a barrier that reduces a moving speed of a holewhen the hole moves from the second HTL 322 to the second EML 324.Therefore, a balance of electrons and holes may be adjusted in thesecond EML 324. The absolute value of the HOMO energy level of the ECL323 may be within a range of 5.20 eV to 5.60 eV. The absolute value ofthe HOMO energy level of the second HTL 322 may be within a range of5.10 eV to 5.50 eV. Therefore, the absolute value of the HOMO energylevel of the ECL 323 may be adjusted 0.10 eV to 0.50 eV higher than theabsolute value of the HOMO energy level of the second HTL 322 in orderthat the ECL 323 has an energy barrier. Also, the ECL 323 may be formedof 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD),2,9-dimethyl-4,7-diphenyl-1,10-phenthroline (BCP),2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi),and/or the like, but is not limited thereto. This will be describedbelow with reference to FIG. 7.

FIG. 7 is a diagram showing an energy band diagram according to thethird embodiment of the present disclosure.

As shown in FIG. 7, an electron (e−) supplied through the second ETL 326and a hole (h+) supplied through the second HTL 322 may be recombined inthe second EML 324 to generate an exciton. A combination area where anelectron and a hole are combined in the second EML 324 may be referredto as an emission area (an emission zone) or a recombination area (arecombination zone).

Moreover, an absolute value of a HOMO energy level of the ECL 323 may beadjusted greater than an absolute value of an HOMO energy level of thesecond HTL 322, and thus, the ECL 323 may act as a barrier that reducesa moving speed of a hole when the hole moves from the second HTL 322 tothe second EML 324. Therefore, since a balance of electrons and holes isformed in the second EML 324 by the ECL 323, lifetime is enhanced, anexciton generated by a recombination of an electron and a hole isconfined in the second EML 324, thereby enhancing lifetime.

Moreover, a hole mobility of the ECL 323 may be adjusted 1.0×10⁻¹ to1.0×10⁻² times lower than that of the second HTL 322. That is, the holemobility of the ECL 323 may be within a range of 1.0×10⁻⁵ cm²/Vs to1.0×10⁻⁶ cm²Ns. The hole mobility of the second HTL 322 may be within arange of 1.0×10⁻⁴ cm²/Vs to 1.0×10⁻⁵ cm²/Vs. Since the hole mobility ofthe ECL 323 is adjusted lower than that of the second HTL 322, a movingspeed of a hole which moves from the second HTL 322 to the second EML324 may be adjusted, and thus, a balance of an electron and a hole inthe second EML 324 may be adjusted. Therefore, a movement of an emissionarea of the second EML 324 caused by the elapse of time is minimized bythe ECL 323, a distribution of the emission area is widened, and aproblem where lifetime is reduced by the elapse of time is solved. Also,the ECL 323 may have a thickness of about 5 nm to 20 nm. If a thicknessof the ECL 323 is less than about 5 nm, efficiency is reduced, and if athickness of the ECL 323 is more than about 20 nm, a thickness of theorganic light emitting device is increased, causing an increase in thedriving voltage or a reduction in efficiency or lifetime.

A driving voltage, efficiency, and lifetime in the third embodiment ofthe present disclosure will be described below with reference to thefollowing Table 2 and FIG. 9.

Moreover, a CGL 340 may be formed between the first emission part 310and the second emission part 320. The CGL 340 may adjust a chargebalance between the first emission part 310 and the second emission part320 and may include an N-type CGL and/or a P-type CGL. The N-type CGLmay inject an electron into the first EML 314 and may be formed of anorganic layer doped with metal and/or the like, but is not limitedthereto. Also, the P-type CGL may inject a hole into the second EML 324and may be formed of an organic layer including a P-type dopant, but isnot limited thereto.

The first EML 314 and the second EML 324 may be EMLs that emit lighthaving the same color, respectively. For example, each of the first EML314 and the second EML 324 may be one of a red EML, a green EML, and ablue EML. Therefore, the organic light emitting device according to anembodiment of the present disclosure may be a monocolor light emittingdevice that emits light having the same color. Alternatively, the firstEML 314 and the second EML 324 may be emission layers that emit lighthaving different colors. For example, the first EML 314 may be one of ared EML, a green EML, and a blue EML, and the second EML 324 may be anEML having a color that differs from that of the first EML 314. Also,the first EML 314 and the second EML 324 may be substantially the sameas the first EML 214 and second EML 224 of FIG. 4, and thus, theirdetailed descriptions are not provided.

Moreover, in the third embodiment of the present disclosure, the organiclight emitting device including two emission parts has been described asan example, but the above-described details may be applied to an organiclight emitting device including three or more emission parts. Even inthis case, the ETL and the ECL according to the third embodiment of thepresent disclosure may be applied.

Moreover, in the third embodiment of the present disclosure, the ECL 323has been described above as being included in the second emission part320, but is not limited thereto. In other embodiments, an ECL may beprovided in the first emission part 310, and the ECL included in thefirst emission part 310 may be provided between the first HTL 312 andthe first EML 314 and may have the same characteristic as that of theECL 323 included in the second emission part 320. In this case, thefirst emission part 310 may be configured with the first ETL 316 havingthe same characteristic as that of the second ETL 326. Therefore, atleast one among the first and second emission parts 310 and 320 mayinclude an ETL and an ECL which each include two materials havingdifferent absolute values of LUMO energy levels. This will be describedbelow with reference to FIG. 8.

FIG. 8 is a diagram illustrating an organic light emitting device 400according to a fourth embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 8, the organic light emitting device 400 according tothe fourth embodiment of the present disclosure may include an emissionpart 1180 between a first electrode 402 and a second electrode 404. Theemission part 1180 may include a first emission part 410 and a secondemission part 420. A substrate 401, the first electrode 402, theemission part 1180, and the second electrode 404 illustrated in FIG. 8may be substantially the same as the substrate 201, the first electrode202, the emission part 1180, and the second electrode 204 describedabove with reference to FIG. 4. Thus, detailed descriptions of thesubstrate 401, the first electrode 402, the emission part 1180, and thesecond electrode 404 illustrated in FIG. 8 are not provided.

The first emission part 410 may include a first HTL 412, a first EML414, a first ECL 413, and a first ETL 416 which are disposed on thefirst electrode 402.

A hole supplied through the first HTL 412 and the first ECL 413 and anelectron supplied through the first ETL 416 may be recombined in thefirst EML 414 to generate an exciton. An area where the exciton isgenerated in the first EML 414 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an HIL may be further formed on the first electrode 402. TheHIL may smoothly transfer a hole, supplied from the first electrode 402,to the first HTL 412. Also, the first HTL 412 may be a P-type HTL dopedwith a P-type dopant.

The first ECL 413 may be disposed under the first EML 414 and betweenthe first HTL 412 and the first EML 414.

Moreover, the second emission part 420 which includes a second HTL 422,a second EML 424, a second ECL 423, and a second ETL 426 may be formedon the first emission part 410.

A hole supplied through the second HTL 422 and the second ECL 423 and anelectron supplied through the second ETL 426 may be recombined in thesecond EML 424 to generate an exciton. An area where the exciton isgenerated in the second EML 424 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an EIL may be further formed on the second ETL 426. The EILmay smoothly transfer an electron, supplied from the second electrode404, to the second ETL 426.

The second ECL 423 may be disposed between the second HTL 422 and thesecond EML 424.

The first HTL 412, the second HTL 422, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 414 and thesecond EML 424. Also, the first ETL 416, the second ETL 426, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 414 and the second EML 424.

The first ETL 416 and the second ETL 426 may each be formed of twomaterials having different absolute values of LUMO energy levels, and byadjusting a content of the two materials, the first ETL 416 and thesecond ETL 426 may each be configured in order to reduce electronmobility. That is, an absolute value of a LUMO energy level of a firstmaterial of two different materials is adjusted higher than an absolutevalue of a LUMO energy level of a second material, and thus, an electronis easily injected into the first EML 414 and the second EML 424. Theabsolute value of the LUMO energy level of the first material may have arange of 2.91 eV to 3.40 eV, and the absolute value of the LUMO energylevel of the second material may have a range of 2.60 eV to 2.90 eV.Also, the first material is one among materials having an absolute valueof a LUMO energy level which is within a range of 2.91 eV to 3.40 eV.For example, the first material may be one among anthracene derivatives,triazine derivatives, and carbozole derivatives, but is not limitedthereto. The second material is one among materials having an absolutevalue of a LUMO energy level which is within a range of 2.60 eV to 2.90eV, and for example, may include 8-hydroxyquinolinolato-lithium (Liq).Also, the first material and the second material may be mixed throughco-deposition.

Moreover, a content of the second material is adjusted higher than thatof the first material, or the second material having the absolute valueof the LUMO energy level which is less than the absolute value of theLUMO energy level of the first material is configured higher in contentthan the first material, and thus, an electron mobility of each of thefirst ETL 416 and the second ETL 426 is lowered, whereby an emissionarea where a balance of electrons and holes is formed is located in eachof the first EML 414 and the second EML 424. Therefore, a lifetime ofeach of the first EML 414 and the second EML 424 is enhanced. That is,since Liq which is the second material is configured higher in contentthan the first material, electron mobility is lowered, and thus, theemission area where a balance of electrons and holes is formed islocated in each of the first EML 414 and the second EML 424, therebyenhancing lifetime. Also, a content of the second material exceeds 50 wt% in the first ETL 416 and the second ETL 426. Also, the first ETL 416and the second ETL 426 may each have a thickness of about 10 nm to 40nm. If a thickness of each of the first ETL 416 and the second ETL 426is less than about 10 nm, each of the first ETL 416 and the second ETL426 cannot act an ETL, and if a thickness of each of the first ETL 416and the second ETL 426 is more than about 40 nm, a thickness of theorganic light emitting device is increased, causing an increase in thedriving voltage or a reduction in efficiency or lifetime.

The first and second ECLs 413 and 423 may be provided in at least oneamong the first emission part 410 and the second emission part 420.Also, the first and second ECLs 413 and 423 may be disposed under thefirst EML 414 and the second EML 424.

The first and second ECLs 413 and 423 may each be formed of twomaterials which have different absolute values in LUMO energy level, andmay be provided in an emission part including the first and second ETLs416 and 426 formed of two materials. Therefore, provided is an organiclight emitting display device in which a balance of electrons and holesis adjusted in the first and second EMLs 414 and 424, lifetime is stablyreduced as time elapses, and lifetime is long. That is, if the first andsecond ETLs 416 and 426 and the first and second ECLs 413 and 423 areall provided, lifetime is further enhanced, and lifetime linearlychanges without being changed to a bell shape as time elapses, therebyproviding an organic light emitting display device having long lifetime.

An absolute value of a HOMO energy level of the first ECL 413 may beadjusted greater than an absolute value of a HOMO energy level of thefirst HTL 412, and thus, the first ECL 413 may act as a barrier thatreduces a moving speed of a hole when the hole moves from the first HTL412 to the first EML 414. Therefore, a balance of electrons and holes isformed in the first EML 414. Accordingly, since a balance of electronsand holes is formed in the first EML 414 by the first ECL 413, lifetimeis enhanced, an exciton generated by a recombination of an electron anda hole is confined in the first EML 414, thereby enhancing lifetime.

The absolute value of the HOMO energy level of the first ECL 413 may bewithin a range of 5.20 eV to 5.60 eV. The absolute value of the HOMOenergy level of the first HTL 412 may be within a range of 5.10 eV to5.50 eV. Therefore, the absolute value of the HOMO energy level of thefirst ECL 413 may be adjusted 0.10 eV to 0.50 eV higher than theabsolute value of the HOMO energy level of the first HTL 412 in orderthat the first ECL 413 has an energy barrier. Also, the first ECL 413may be formed of 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole(PBD), 2,9-dimethyl-4,7-diphenyl-1,10-phenthroline (BCP),2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi),and/or the like, but is not limited thereto.

Moreover, a hole mobility of the first ECL 413 may be adjusted 1.0×10⁻¹to 1.0×10⁻² times lower than that of the first HTL 412. That is, thehole mobility of the first ECL 413 may be within a range of 1.0×10⁻⁵cm²/Vs to 1.0×10⁻⁶ cm²/Vs. The hole mobility of the first HTL 412 may bewithin a range of 1.0×10⁻⁴ cm²/Vs to 1.0×10⁻⁵ cm²/Vs. Since the holemobility of the first ECL 413 is adjusted lower than that of the firstHTL 412, a moving speed of a hole which moves from the first HTL 412 tothe first EML 414 may be adjusted, and thus, a balance of electrons andholes in the first EML 414 may be adjusted. Therefore, a movement of anemission area of the first EML 414 caused by the elapse of time isminimized by the first ECL 413, a distribution of the emission area iswidened, and a problem where lifetime is reduced by the elapse of timeis solved.

The first ECL 413 may have a thickness of about 5 nm to 20 nm. If athickness of the first ECL 413 is less than about 5 nm, efficiency isreduced, and if a thickness of the first ECL 413 is more than about 20nm, a thickness of the organic light emitting device is increased,causing an increase in the driving voltage or a reduction in efficiencyor lifetime.

The second ECL 423 may be disposed between the second HTL 422 and thesecond EML 424. An absolute value of a HOMO energy level of the secondECL 423 may be adjusted greater than an absolute value of an HOMO energylevel of the second HTL 422, and thus, the second ECL 423 may act as abarrier that reduces a moving speed of a hole when the hole moves fromthe second HTL 422 to the second EML 424. Therefore, a balance ofelectrons and holes is formed in the second EML 424. Accordingly, sincea balance of electrons and holes is adjusted in the second EML 424 bythe second ECL 423, lifetime is enhanced, an exciton generated by arecombination of an electron and a hole is confined in the second EML424, thereby enhancing lifetime.

The absolute value of the HOMO energy level of the second ECL 423 may bewithin a range of 5.20 eV to 5.60 eV. The absolute value of the HOMOenergy level of the second HTL 422 may be within a range of 5.10 eV to5.50 eV. Therefore, the absolute value of the HOMO energy level of thesecond ECL 423 may be adjusted 0.10 eV to 0.50 eV higher than theabsolute value of the HOMO energy level of the second HTL 422 in orderthat the second ECL 423 has an energy barrier. Also, the second ECL 423may be formed of 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole(PBD), 2,9-dimethyl-4,7-diphenyl-1,10-phenthroline (BCP),2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi),and/or the like, but is not limited thereto.

Moreover, a hole mobility of the second ECL 423 may be adjusted 1.0×10⁻¹to 1.0×10⁻² times lower than that of the second HTL 422. That is, thehole mobility of the second ECL 423 may be within a range of 1.0×10⁻⁵cm²/Vs to 1.0×10⁻⁶ cm²/Vs. The hole mobility of the second HTL 422 maybe within a range of 1.0×10⁻⁴ cm²/Vs to 1.0×10⁻⁵ cm²/Vs. Since the holemobility of the second ECL 423 is adjusted lower than that of the secondHTL 422, a moving speed of a hole which moves from the second HTL 422 tothe second EML 424 may be adjusted, and thus, a balance of electrons andholes in the second EML 424 may be adjusted. Therefore, a movement of anemission area of the second EML 424 caused by the elapse of time isminimized by the second ECL 423, a distribution of the emission area iswidened, and a problem where lifetime is reduced by the elapse of timeis solved.

The second ECL 423 may have a thickness of about 5 nm to 20 nm. If athickness of the second ECL 423 is less than about 5 nm, efficiency isreduced, and if a thickness of the second ECL 423 is more than about 20nm, a thickness of the organic light emitting device is increased,causing an increase in the driving voltage or a reduction in efficiencyor lifetime.

Moreover, a CGL 440 may be formed between the first emission part 410and the second emission part 420. The CGL 440 may adjust a chargebalance between the first emission part 410 and the second emission part420 and may include an N-type CGL and/or a P-type CGL. The N-type CGLmay inject an electron into the first EML 414 and may be formed of anorganic layer doped with metal and/or the like, but is not limitedthereto. Also, the P-type CGL may inject a hole into the second EML 424and may be formed of an organic layer including a P-type dopant, but isnot limited thereto.

The first EML 414 and the second EML 424 may be EMLs that emit lighthaving the same color, respectively. For example, each of the first EML414 and the second EML 424 may be one of a red EML, a green EML, and ablue EML. Therefore, the organic light emitting device according to anembodiment of the present disclosure may be a monocolor light emittingdevice that emits light having the same color. Alternatively, the firstEML 414 and the second EML 424 may be emission layers that emit lighthaving different colors. For example, the first EML 414 may be one of ared EML, a green EML, and a blue EML, and the second EML 424 may be anEML having a color that differs from that of the first EML 414. Also,the first EML 414 and the second EML 424 may be substantially the sameas the first EML 214 and second EML 224 of FIG. 4, and thus, theirdetailed descriptions are not provided.

Moreover, in the fourth embodiment of the present disclosure, theorganic light emitting device including two emission parts has beendescribed as an example, but the above-described details may be appliedto an organic light emitting device including three or more emissionparts. Even in this case, the ETL and the ECL according to the fourthembodiment of the present disclosure may be applied.

In a case where an ETL and an ECL are provided, a driving voltage,efficiency, and lifetime will be described below with reference to thefollowing Table 2 and FIG. 9.

The following Table 2 shows a result obtained by measuring a drivingvoltage, efficiency, and color coordinates in experiment examples 4 to7.

TABLE 2 Driving Efficiency Voltage (V) (cd/A) CIEx CIEy Experiment 7.513.7 0.135 0.068 Example 4 Experiment 7.7 14.0 0.135 0.068 Example 5Experiment 7.9 14.0 0.135 0.068 Example 6 Experiment 8.1 13.6 0.1350.068 Example 7

In Table 2, the experiment examples 4 to 7 have been experimented byapplying the organic light emitting device of FIG. 6.

The experiment example 4 is configured identically to the comparativeexample 1. In the experiment example 4, the ECL 323 is formed beforeforming the second EML 324 in a red subpixel area, a green subpixelarea, and a blue subpixel area.

The experiment example 5 is configured identically to the comparativeexample 1. In the experiment example 5, the ECL 323 is formed beforeforming the second EML 324 in a red subpixel area, a green subpixelarea, and a blue subpixel area.

The experiment example 6 is configured identically to the experimentexample 2. In the experiment example 6, the ECL 323 is formed beforeforming the second EML 324 in a red subpixel area, a green subpixelarea, and a blue subpixel area.

The experiment example 7 is configured identically to the experimentexample 3. In the experiment example 7, the ECL 323 is formed beforeforming the second EML 324 in a red subpixel area, a green subpixelarea, and a blue subpixel area.

In Table 2, color coordinates (CIEx, CIEy) represent blue colorcoordinates (0.135, 0.068). Table 2 shows a result that is obtained bycomparing the driving voltages (V) and the efficiencies (cd/A) withrespect to a current density of 5 mA/cm² in a state where the blue colorcoordinates are identically set.

To describe the driving voltages (V), as shown in Table 2, it can beseen that in the driving voltages (V), the experiment examples 5 to 7increase a little in comparison with the experiment example 4.

To describe the efficiencies (cd/A), since an ECL is further provided inan ETL, it can be seen that the experiment examples 4 to 7 are enhancedfurther in efficiency than the comparative example 1 and the experimentexamples 1 to 3. That is, it can be seen that efficiency is furtherenhanced in the experiment example 6, where an ETL and an ECL eachinclude a first material having an absolute value of a LUMO energy levelgreater than an absolute value of a LUMO energy level of Liq (a secondmaterial) and in which a content of the first material is equal to thatof the second material, than the experiment 4 where the ETL and the ECLeach include a first material having an absolute value of a LUMO energylevel less than the absolute value of the LUMO energy level of Liq (thesecond material) and in which a content of the first material is equalto that of the second material. Through this, it can be seen thatefficiency is further enhanced when the ETL is formed of a materialhaving an absolute value of a LUMO energy level greater than theabsolute value of the LUMO energy level of Liq, and the ECL is furtherformed. Also, it can be seen that the experiment examples 5 and 6increase further in efficiency than the experiment example 7. Throughthis, it can be seen that efficiency further increases in the experimentexamples 5 and 6, where a content of the second material is equal to orlower than that of the first material, than the experiment example 7where a content of the second material is higher than that of the firstmaterial.

Lifetime will be described below with reference to FIG. 9. A lifetimemeasurement result shown in FIG. 9 has been obtained through measurementfor an experiment, and a measured lifetime does not limit details of thepresent disclosure. Therefore, FIG. 9 shows a result obtained measuringlifetime for checking whether lifetime is enhanced under conditions ofthe experiment examples 4 to 7.

FIG. 9 is a diagram showing lifetimes in the experiment examples 4 to 7of the present disclosure.

In FIG. 9, the abscissa axis indicates time (hr), and the ordinate axisindicates a luminance drop rate (%). Also, the experiment example 4 isreferred to as D, the experiment example 5 is referred to as E, theexperiment example 6 is referred to as F, and the experiment example 7is referred to as G.

As shown in FIG. 9, when initial emission luminance is 100%, it can beseen that in time (i.e., a 95% lifetime (T95) of the organic lightemitting device) taken until luminance is reduced by 95%, the experimentexamples 4 and 5 are about 220 hours, the experiment example 6 is about320 hours, and the experiment example 7 is about 1,000 hours. Therefore,it can be seen that the lifetime of the experiment example 7 increasesby about 4.5 times lifetime of the experiment example 4. That is, it canbe seen that lifetime is far more enhanced in the experiment example 7,where a content of the second material is higher than that of the firstmaterial, than the experiment examples 4 to 6.

Moreover, FIG. 9 shows blue lifetime, and a total lifetime of theorganic light emitting display device is enhanced further in theexperiment example 7 than the experiment examples 4 to 6.

In the third embodiment of the present disclosure, the ECL is provided,and efficiency, a driving voltage, and lifetime based on a content ofthe first material and the second material included in the ETL will bedescribed below. It can be seen that efficiency further increases in theexperiment examples 5 and 6, where a content of the second material isequal to or lower than that of the first material, than the experimentexample 7 where a content of the second material is higher than that ofthe first material. It can be seen that the driving voltage increases alittle more in the experiment example 7, where a content of the secondmaterial is higher than that of the first material, than the experimentexamples 5 and 6 where a content of the second material is equal to orlower than that of the first material. Therefore, it can be seen thatthe driving voltage increases a little more, efficiency is reduced alittle more, and lifetime is further enhanced in a case, where the ECLis provided and a content of the second material is higher than that ofthe first material, than a case where a content of the second materialis equal to or lower than that of the first material. That is, incomparison with FIG. 5 showing a case where an ETL including twomaterials having different mobility in the second embodiment of thepresent disclosure, it can be seen that as time elapses, lifetime isreduced, namely, a bell shape is not shown. Accordingly, it can be seenthat lifetime is further enhanced when an ETL is formed of two materialshaving different absolute values of LUMO energy levels, a materialhaving a relatively smaller absolute value of a LUMO energy level amongthe two materials is higher in content than a material having arelatively larger absolute value of a LUMO energy level, and an ECL isprovided. That is, it can be seen that as time elapses, a bell-shapedlifetime becomes linear, and thus, lifetime is further improved.

The third embodiment of the present disclosure has been described abovewith reference to Table 2 and FIG. 9, but according to the fourthembodiment of the present disclosure where an ETL and an ECL arerespectively applied to two emission parts, a lifetime of an organiclight emitting display device is also enhanced.

An energy band diagram and an emission distribution with respect totime, according to the second and third embodiments of the presentdisclosure, will be described below. Details where lifetime is enhancedby an ETL or an ETL and an ECL according to an embodiment of the presentdisclosure will be described below with reference to FIGS. 10A and 10B.

FIG. 10A is a diagram showing an energy band diagram according to thesecond embodiment of the present disclosure and an energy band diagramaccording to the third embodiment of the present disclosure. Referencenumerals in the second embodiment of the present disclosure may beapplied to FIG. 10A.

As shown in FIG. 10A, an electron (e−) supplied through the second ETL226 and a hole (h+) supplied through the second HTL 222 may berecombined in the second EML 224 to generate an exciton. A combinationarea where an electron and a hole are combined in the second EML 224 maybe referred to as an emission area (an emission zone) or a recombinationarea (a recombination zone). In FIG. 10A, an arrow indicates that timeincreases.

In FIG. 10A, {circle around (1)} refers to the experiment example 3 ofthe second embodiment of the present disclosure, and the second ETL 226is formed of at least two materials. In this case, the second ETL 226 isconfigured through co-deposition so that an absolute value of a LUMOenergy level of a first material is larger than an absolute value of aLUMO energy level of a second material, and a content of the secondmaterial is higher than that of the first material. Also, {circle around(2)} refers to the experiment example 7 of the third embodiment of thepresent disclosure, and in this case, the second ETL 226 of theexperiment example 3 of the second embodiment of the present disclosureis provided, and an ECL is provided between the second EML 224 and thesecond HTL 222.

As shown in FIG. 10A, in {circle around (1)} and {circle around (2)}, itcan be seen that as time elapses, an emission area of the second EML 224is located in the second EML 224. That is, in embodiments 2 and 3 of thepresent disclosure where an ETL is formed of two materials havingdifferent absolute values of LUMO energy levels, it can be seen that theemission area of the second EML 224 is not close to the second HTL 222but is located in the second EML 224. Also, it can be seen that as timeelapses, an emission position does not change. Also, it can be seen thatas time elapses, a non-emission area does not appear.

FIG. 10B is a diagram showing an emission distribution with respect totime in an emission area according to the second embodiment and thethird embodiment of the present disclosure.

As shown in FIG. 10B, it can be seen that an emission distribution iswider in {circle around (2)} than {circle around (1)}. That is, it canbe seen that despite the elapse of time, the emission distribution iswider in {circle around (2)} than {circle around (1)} due to an ECL.

As described above with reference to FIGS. 10A and 10B, in the secondembodiment of the present disclosure, it can be seen that due to an ETLwhere an absolute value of a LUMO energy level of a first material islarger than an absolute value of a LUMO energy level of a secondmaterial, and a content of the second material is higher than that ofthe first material, as time elapses, a non-emission area does notappear, and an emission position is maintained. Also, in the thirdembodiment of the present disclosure where the ETL of the secondembodiment of the present disclosure and ECL are provided, since theemission area is widened as time elapses, lifetime is not reduceddespite the elapse of time, namely, despite the elapses of a long time,and thus, lifetime is further enhanced.

The emission positions and the emission distributions according to thesecond and third embodiments of the present disclosure have beendescribed above with reference to FIGS. 10A and 10B. However, even in acase where the fourth embodiment of the present disclosure is applied,as time elapses, an emission position is maintained, and an emissionarea is widened, whereby lifetime is not reduced despite the elapse oftime.

In the second to fourth embodiments of the present disclosure, theorganic light emitting display device where lifetime is enhanced byadjusting a LUMO energy level included in an ETL has been describedabove. The present disclosure proposes an organic light emitting displaydevice where lifetime is enhanced by adjusting a LUMO energy level of anETL and a LUMO energy level of a CGL adjacent to the ETL. This will bedescribed below with reference to FIG. 11.

FIG. 11 is a diagram illustrating an organic light emitting device 500according to a fifth embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 11, the organic light emitting device 500 according tothe fifth embodiment of the present disclosure may include a substrate501, first and second electrodes 502 and 504, and an emission part 1180between the first and second electrodes 502 and 504. The emission part1180 may include a first emission part 510 and a second emission part520. The substrate 501, the first electrode 502, the emission part 1180,and the second electrode 504 illustrated in FIG. 11 may be substantiallythe same as the substrate 201, the first electrode 202, the emissionpart 1180, and the second electrode 204 described above with referenceto FIG. 4. Thus, detailed descriptions of the substrate 501, the firstelectrode 502, the emission part 1180, and the second electrode 504illustrated in FIG. 11 are not provided.

The first emission part 510 may include a first HTL 512, a first EML514, and a first ETL 516 which are disposed on the first electrode 502.A hole supplied through the first HTL 512 and an electron suppliedthrough the first ETL 516 may be recombined in the first EML 514 togenerate an exciton. An area where the exciton is generated in the firstEML 514 may be referred to as a recombination area (a recombinationzone) or an emission area (an emission zone).

Moreover, an HIL may be further formed on the first electrode 502. TheHIL may smoothly transfer a hole, supplied from the first electrode 502,to the first HTL 512. Also, the first HTL 512 may be a P-type HTL dopedwith a P-type dopant.

Moreover, the second emission part 520 which includes a second HTL 522,a second EML 524, and a second ETL 526 may be formed on the firstemission part 510.

A hole supplied through the second HTL 522 and an electron suppliedthrough the second ETL 526 may be recombined in the second EML 524 togenerate an exciton. An area where the exciton is generated in thesecond EML 524 may be referred to as a recombination area (arecombination zone) or an emission area (an emission zone).

The second ETL 526 may be formed of one amongtris(8-hydroxy-quinolinato)aluminum (Alq₃),3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ),8-hydroxyquinolinolato-lithium (Liq), anthracene derivatives, triazinederivatives, and carbozole derivatives, but is not limited thereto.

Moreover, an EIL may be further formed on the second ETL 526. The EILmay smoothly transfer an electron, supplied from the second electrode504, to the second ETL 526.

The first HTL 512, the second HTL 522, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 514 and thesecond EML 524. Also, the first ETL 516, the second ETL 526, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 514 and the second EML 524.

Moreover, a CGL 540 may be formed between the first emission part 510and the second emission part 520. The CGL 540 may adjust a chargebalance between the first emission part 510 and the second emission part520 and may include an N-type CGL 541 and a P-type CGL 542. The N-typeCGL 541 may inject an electron into the first EML 514 and may be formedof an organic layer doped with metal and/or the like, but is not limitedthereto. Also, the P-type CGL 542 may inject a hole into the second EML524 and may be formed of an organic layer including a P-type dopant, butis not limited thereto.

The first EML 514 and the second EML 524 may be EMLs that emit lighthaving the same color. For example, each of the first EML 514 and thesecond EML 524 may be one among a red EML, a green EML, and a blue EML.Therefore, the organic light emitting device according to an embodimentof the present disclosure may be a monocolor light emitting device thatemits light having the same color. Alternatively, the first EML 514 andthe second EML 524 may be EMLs that emit light having different colors.For example, the first EML 514 may be one among a red EML, a green EML,and a blue EML, and the second EML 524 may be an EML having a color thatdiffers from that of the first EML 514. Also, the first EML 514 and thesecond EML 524 may be substantially the same as the first EML 214 andsecond EML 224 of FIG. 4, and thus, their detailed descriptions are notprovided.

Moreover, an energy bandgap of the N-type CGL 541 adjacent to the firstETL 516 may be adjusted for adjusting an electron mobility of the firstETL 516. That is, an energy bandgap of the first ETL 516 may beconfigured higher than an energy bandgap of a host included in theN-type CGL 541, and thus, the electron mobility of the first ETL 516 isreduced.

Therefore, the energy bandgap of the first ETL 516 may be configured0.50 eV higher than an energy bandgap of a host included in the N-typeCGL 541, for adjusting the electron mobility of the first ETL 516. Thatis, the energy bandgap of the first ETL 516 may be configured 0.50 eV to1.00 eV higher than the energy bandgap included in the N-type CGL 541.Here, the energy bandgap may denote a difference between an absolutevalue of a HOMO energy level and an absolute value of a LUMO energylevel. That is, an absolute value of a HOMO energy level of a hostincluded in the N-type CGL 541 may be 5.80 eV, an absolute value of aLUMO energy level may be within a range of 2.90 eV to 3.20 eV, and anenergy bandgap may be within a range of 2.60 eV to 2.90 eV. Also, anabsolute value of a HOMO energy level of the first ETL 516 may be 5.60eV, an absolute value of a LUMO energy level may be within a range of2.00 eV to 2.50 eV, and an energy bandgap may be within a range of 3.10eV to 3.60 eV. Therefore, the first ETL 516 may include a materialhaving an absolute value of a LUMO energy level which is within a rangeof 2.00 eV to 2.50 eV, and for example, the material may be one amonganthracene derivatives, triazine derivatives, and carbozole derivatives.Also, a host included in the N-type CGL 541 may include a materialhaving an absolute value of a LUMO energy level which is within a rangeof 2.90 eV to 3.20 eV, and for example, the material may be anthracenederivatives. Also, the first ETL 516 may have a thickness of about 5 nmto 30 nm. If a thickness of the first ETL 516 is less than about 5 nm,the first ETL 516 cannot act as an ETL, and if a thickness of the firstETL 516 is more than about 30 nm, a thickness of the organic lightemitting device is increased, causing an increase in the driving voltageor a reduction in efficiency or lifetime.

Therefore, since the electron mobility of the first ETL 516 is reduced,a balance of electrons and holes in the first EML 514 may be adjusted,thereby enhancing lifetime.

Moreover, in the fifth embodiment of the present disclosure, the organiclight emitting device including two emission parts has been described asan example, but the above-described details may be applied to an organiclight emitting device including three or more emission parts. Even inthis case, the ETL according to the fifth embodiment of the presentdisclosure may be applied.

FIG. 12 is a diagram illustrating an organic light emitting device 600according to a sixth embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 12, the organic light emitting device 600 according tothe sixth embodiment of the present disclosure may include a substrate601, first and second electrodes 602 and 604, and an emission part 1180between the first and second electrodes 602 and 604. The emission part1180 may include a first emission part 610 and a second emission part620. The substrate 601, the first electrode 602, the emission part 1180,and the second electrode 604 illustrated in FIG. 12 may be substantiallythe same as the substrate 201, the first electrode 202, the emissionpart 1180, and the second electrode 204 described above with referenceto FIG. 4. Thus, detailed descriptions of the substrate 601, the firstelectrode 602, the emission part 1180, and the second electrode 604illustrated in FIG. 12 are not provided.

The first emission part 610 may include a first HTL 612, an ECL 613, afirst EML 614, and a first ETL 616 which are disposed on the firstelectrode 602.

A hole supplied through the first HTL 612 and the ECL 613 and anelectron supplied through the first ETL 616 may be recombined in thefirst EML 614 to generate an exciton. An area where the exciton isgenerated in the first EML 614 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an HIL may be further formed on the first electrode 602. TheHIL may smoothly transfer a hole, supplied from the first electrode 602,to the first HTL 612. Also, the first HTL 612 may be a P-type HTL dopedwith a P-type dopant.

Moreover, the second emission part 620 which includes a second HTL 622,a second EML 624, and a second ETL 626 may be formed on the firstemission part 610.

A hole supplied through the second HTL 622 and an electron suppliedthrough the second ETL 626 may be recombined in the second EML 624 togenerate an exciton. An area where the exciton is generated in thesecond EML 624 may be referred to as a recombination area (arecombination zone) or an emission area (an emission zone).

The second ETL 626 may be formed of one amongtris(8-hydroxy-quinolinato)aluminum (Alq₃),3-(4-biphenyl)-4-phenyl-5-tert-butylpneyl-1,2,4-triazole (TAZ),8-hydroxyquinolinolato-lithium (Liq), anthracene derivatives, triazinederivatives, and carbozole derivatives, but is not limited thereto.

Moreover, an EIL may be further formed on the second ETL 626. The EILmay smoothly transfer an electron, supplied from the second electrode604, to the second ETL 626.

The first HTL 612, the second HTL 622, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 614 and thesecond EML 624. Also, the first ETL 616, the second ETL 626, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 614 and the second EML 624.

Moreover, a CGL 640 may be formed between the first emission part 610and the second emission part 620. The CGL 640 may adjust a chargebalance between the first emission part 610 and the second emission part620 and may include an N-type CGL 641 and a P-type CGL 642. The N-typeCGL 641 may inject an electron into the first EML 614 and may be formedof an organic layer doped with metal and/or the like, but is not limitedthereto. Also, the P-type CGL 642 may inject a hole into the second EML624. The P-type CGL 642 may be formed of an organic layer including aP-type dopant, but is not limited thereto.

The first EML 614 and the second EML 624 may be EMLs that emit lighthaving the same color. For example, each of the first EML 614 and thesecond EML 624 may be one among a red EML, a green EML, and a blue EML.Therefore, the organic light emitting device according to an embodimentof the present disclosure may be a monocolor light emitting device thatemits light having the same color. Alternatively, the first EML 614 andthe second EML 624 may be EMLs that emit light having different colors.For example, the first EML 614 may be one among a red EML, a green EML,and a blue EML, and the second EML 624 may be an EML having a color thatdiffers from that of the first EML 614. Also, the first EML 614 and thesecond EML 624 may be substantially the same as the first EML 214 andsecond EML 224 of FIG. 4, and thus, their detailed descriptions are notprovided.

The first ETL 616 may be substantially the same as the first ETL 516described above with reference to FIG. 11, and thus, its detaileddescription is omitted or will be brief.

The ECL 613 may be provided in an emission part including the first ETL616 having an energy bandgap shifted higher than that of a host includedin the CGL 640. Therefore, provided is an organic light emitting displaydevice in which a balance of electrons and holes is adjusted in thefirst EML 614, lifetime is stably reduced as time elapses, and lifetimeis long. That is, if the first ETL 616 and the ECL 613 are all provided,lifetime is further enhanced, and lifetime linearly changes withoutbeing changed to a bell shape as time elapses, thereby providing anorganic light emitting display device having long lifetime.

The ECL 613 may be disposed under the first EML 614 and between thefirst HTL 612 and the first EML 614. A movement of an emission area ofthe first EML 614 caused by the elapse of time is minimized by the ECL613, a distribution of the emission area is widened, and a problem wherelifetime is reduced by the elapse of time is solved.

An energy band diagram of each of the ECL 613, the first ETL 616, andthe N-type CGL 641 will be described below with reference to FIG. 13.

FIG. 13 is a diagram showing an energy band diagram according to thesixth embodiment of the present disclosure.

As shown in FIG. 13, an electron (e−) supplied through the first ETL 616and a hole (h+) supplied through the first HTL 612 and the ECL 613 maybe recombined in the first EML 614 to generate an exciton. A combinationarea where an electron and a hole are combined in the first EML 614 maybe referred to as an emission area (an emission zone) or a recombinationarea (a recombination zone).

As illustrated in FIG. 13, a difference (ΔE) between an energy bandgapof the first ETL 616 and an energy bandgap included in the N-type CGL641 may be adjusted to 0.50 eV to 1.00 eV for adjusting an electronmobility of the first ETL 616. Therefore, a balance of electrons andholes in the first EML 614 may be formed by reducing the electronmobility of the first ETL 616, thereby enhancing lifetime.

Moreover, an absolute value of a HOMO energy level of the ECL 613 may beadjusted greater than an absolute value of an HOMO energy level of thefirst HTL 612, and thus, the ECL 613 may act as a barrier that reduces amoving speed of a hole when the hole moves from the first HTL 612 to thefirst EML 614. Therefore, since a balance of electrons and holes isformed in the first EML 614 by the ECL 613, lifetime is enhanced, anexciton generated by a recombination of an electron and a hole isconfined in the first EML 614, thereby enhancing lifetime.

An absolute value of a HOMO energy level of the ECL 613 may be within arange of 5.20 eV to 5.60 eV. An absolute value of a HOMO energy level ofthe first HTL 612 may be within a range of 5.10 eV to 5.50 eV.Therefore, the absolute value of the HOMO energy level of the ECL 613may be adjusted 0.10 eV to 0.50 eV higher than the absolute value of theHOMO energy level of the first HTL 612 in order for the ECL 613 to havean energy barrier. Also, a hole mobility of the ECL 613 may be adjusted1.0×10⁻¹ to 1.0×10⁻² times lower than that of the first HTL 612. Thatis, the hole mobility of the ECL 613 may be within a range of 1.0×10⁻⁵cm²/Vs to 1.0×10⁻⁶ cm²/Vs. The hole mobility of the first HTL 612 may bewithin a range of 1.0×10⁻⁴ cm²/Vs to 1.0×10⁻⁵ cm²/Vs. Since the holemobility of the ECL 613 is adjusted lower than that of the first HTL612, a moving speed of a hole which moves from the first HTL 612 to thefirst EML 614 may be adjusted, and thus, a balance of electrons andholes in the first EML 614 may be adjusted. Therefore, a movement of anemission area of the first EML 614 caused by the elapse of time isminimized by the ECL 613, a distribution of the emission area iswidened, and a problem where lifetime is reduced by the elapse of timeis solved.

FIG. 14 is a diagram illustrating an organic light emitting device 700according to a seventh embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 14, the organic light emitting device 700 according tothe seventh embodiment of the present disclosure may include a substrate701, first and second electrodes 702 and 704, and an emission part 1180between the first and second electrodes 702 and 704. The emission part1180 may include a first emission part 710 and a second emission part720. The substrate 701, the first electrode 702, the emission part 1180,and the second electrode 704 illustrated in FIG. 14 may be substantiallythe same as the substrate 201, the first electrode 202, the emissionpart 1180, and the second electrode 204 described above with referenceto FIG. 4. Thus, detailed descriptions of the substrate 701, the firstelectrode 702, the emission part 1180, and the second electrode 704illustrated in FIG. 14 are not provided.

The first emission part 710 may include a first HTL 712, a first EML714, and a first ETL 716 which are disposed on the first electrode 702.A hole supplied through the first HTL 712 and an electron suppliedthrough the first ETL 716 may be recombined in the first EML 714 togenerate an exciton. An area where the exciton is generated in the firstEML 714 may be referred to as a recombination area (a recombinationzone) or an emission area (an emission zone).

Moreover, an HIL may be further formed on the first electrode 702. TheHIL may smoothly transfer a hole, supplied from the first electrode 702,to the first HTL 712. Also, the first HTL 712 may be a P-type HTL dopedwith a P-type dopant.

Moreover, the second emission part 720 which includes a second HTL 722,a second EML 724, an ECL 723, and a second ETL 726 may be formed on thefirst emission part 710.

A hole supplied through the second HTL 722 and the ECL 723 and anelectron supplied through the second ETL 726 may be recombined in thesecond EML 724 to generate an exciton. An area where the exciton isgenerated in the second EML 724 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an EIL may be further formed on the second ETL 726. The EILmay smoothly transfer an electron, supplied from the second electrode704, to the second ETL 726.

The first HTL 712, the second HTL 722, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 714 and thesecond EML 724. Also, the first ETL 716, the second ETL 726, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 714 and the second EML 724.

The second ETL 726 may be substantially the same as the second ETL 326described above with reference to FIG. 6, and thus, its detaileddescription is omitted.

The ECL 723 may be provided in one among the first emission part 710 andthe second emission part 720. The ECL 723 may be provided in the secondemission part 720. The ECL 723 may be disposed under the first EML 724and between the second HTL 722 and the second EML 724.

Moreover, the ECL 723 may be formed of two materials which havedifferent absolute values in LUMO energy level, and may be provided inan emission part including the second ETL 726 formed of two materials.Therefore, provided is an organic light emitting display device in whicha balance of electrons and holes is adjusted in the second EML 724,lifetime is stably reduced as time elapses, and lifetime is long. Thatis, if the second ETL 726 and the ECL 723 are all provided, lifetime isfurther enhanced, and lifetime linearly changes without being changed toa bell shape as time elapses, thereby providing an organic lightemitting display device having long lifetime.

The ECL 723 may be substantially the same as the ECL 323 described abovewith reference to FIG. 6, and thus, its detailed description is omitted.

Moreover, a CGL 740 may be formed between the first emission part 710and the second emission part 720. The CGL 740 may adjust a chargebalance between the first emission part 710 and the second emission part720 and may include an N-type CGL 741 and a P-type CGL 742.

The first EML 714 and the second EML 724 may be EMLs that emit lighthaving the same color. For example, each of the first EML 714 and thesecond EML 724 may be one among a red EML, a green EML, and a blue EML.Therefore, the organic light emitting device according to an embodimentof the present disclosure may be a monocolor light emitting device thatemits light having the same color. Alternatively, the first EML 714 andthe second EML 724 may be EMLs that emit light having different colors.For example, the first EML 714 may be one among a red EML, a green EML,and a blue EML, and the second EML 724 may be an EML having a color thatdiffers from that of the first EML 714. Also, the first EML 714 and thesecond EML 724 may be substantially the same as the first EML 214 andsecond EML 224 of FIG. 4, and thus, their detailed descriptions are notprovided.

Moreover, an energy bandgap of the N-type CGL 741 adjacent to the firstETL 716 may be adjusted for adjusting an electron mobility of the firstETL 716. That is, an energy bandgap of the first ETL 716 may beconfigured higher than an energy bandgap of a host included in theN-type CGL 741, and thus, the electron mobility of the first ETL 716 isreduced. The first ETL 716 may be substantially the same as the firstETL 516 described above with reference to FIG. 11, and thus, itsdetailed description is omitted.

A driving voltage, efficiency, and lifetime in the seventh embodiment ofthe present disclosure will be described below with reference to thefollowing Table 3 and FIG. 16.

Moreover, in the seventh embodiment of the present disclosure, theorganic light emitting device including two emission parts has beendescribed as an example, but the above-described details may be appliedto an organic light emitting device including three or more emissionparts. Even in this case, the ETL according to the seventh embodiment ofthe present disclosure may be applied.

FIG. 15 is a diagram illustrating an organic light emitting device 800according to an eighth embodiment of the present disclosure. All thecomponents of the organic light emitting device according to all theembodiments of the present disclosure are operatively coupled andconfigured.

Referring to FIG. 15, the organic light emitting device 800 according tothe eighth embodiment of the present disclosure may include a substrate801, first and second electrodes 802 and 804, and an emission part 1180between the first and second electrodes 802 and 804. The emission part1180 may include a first emission part 810 and a second emission part820. The substrate 801, the first electrode 802, the emission part 1180,and the second electrode 804 illustrated in FIG. 15 may be substantiallythe same as the substrate 201, the first electrode 202, the emissionpart 1180, and the second electrode 204 described above with referenceto FIG. 4. Thus, detailed descriptions of the substrate 801, the firstelectrode 802, the emission part 1180, and the second electrode 804illustrated in FIG. 15 are not provided.

The first emission part 810 may include a first HTL 812, a first ECL813, a first EML 814, and a first ETL 816 which are disposed on thefirst electrode 802. A hole supplied through the first HTL 812 and thefirst ECL 813 and an electron supplied through the first ETL 816 may berecombined in the first EML 814 to generate an exciton. An area wherethe exciton is generated in the first EML 814 may be referred to as arecombination area (a recombination zone) or an emission area (anemission zone).

Moreover, an HIL may be further formed on the first electrode 802. TheHIL may smoothly transfer a hole, supplied from the first electrode 802,to the first HTL 812.

The first ECL 813 may be disposed between the first HTL 812 and thefirst EML 814. The first ECL 813 may be substantially the same as theECL 613 described above with reference to FIGS. 12 and 13, and thus, itsdetailed description is omitted.

Moreover, the second emission part 820 which includes a second HTL 822,a second EML 824, a second ECL 823, and a second ETL 826 may be formedon the first emission part 810.

A hole supplied through the second HTL 822 and the second ECL 823 and anelectron supplied through the second ETL 826 may be recombined in thesecond EML 824 to generate an exciton. An area where the exciton isgenerated in the second EML 824 may be referred to as a recombinationarea (a recombination zone) or an emission area (an emission zone).

Moreover, an EIL may be further formed on the second ETL 826. The EILmay smoothly transfer an electron, supplied from the second electrode804, to the second ETL 826.

The first HTL 812, the second HTL 822, and the HIL may each be referredto as a hole transfer layer. Therefore, the hole transfer layer may be alayer that transfers and injects a hole to the first EML 814 and thesecond EML 824. Also, the first ETL 816, the second ETL 826, and the EILmay each be referred to as an electron transfer layer. Therefore, theelectron transfer layer may be a layer that transfers and injects anelectron to the first EML 814 and the second EML 824.

The second ETL 826 may be substantially the same as the second ETL 326described above with reference to FIG. 6, and thus, its detaileddescription is omitted.

The second ECL 823 may be substantially the same as the ECL 323described above with reference to FIG. 6, and thus, its detaileddescription is omitted.

Moreover, a CGL 840 may be formed between the first emission part 810and the second emission part 820. The CGL 840 may adjust a chargebalance between the first emission part 810 and the second emission part820 and may include an N-type CGL 841 and a P-type CGL 842. The N-typeCGL 841 may inject an electron into the first EML 814 and may be formedof an organic layer doped with metal and/or the like, but is not limitedthereto. Also, the P-type CGL 842 may inject a hole into the second EML824. The P-type CGL 842 may be formed of an organic layer including aP-type dopant, but is not limited thereto.

The first EML 814 and the second EML 824 may be EMLs that emit lighthaving the same color. For example, each of the first EML 814 and thesecond EML 824 may be one among a red EML, a green EML, and a blue EML.Therefore, the organic light emitting device according to an embodimentof the present disclosure may be a monocolor light emitting device thatemits light having the same color. Alternatively, the first EML 814 andthe second EML 824 may be EMLs that emit light having different colors.For example, the first EML 814 may be one among a red EML, a green EML,and a blue EML, and the second EML 824 may be an EML having a color thatdiffers from that of the first EML 814. Also, the first EML 814 and thesecond EML 824 may be substantially the same as the first EML 214 andsecond EML 224 of FIG. 4, and thus, their detailed descriptions are notprovided.

Moreover, an electron mobility of the first ETL 816 may be reduced byadjusting an energy bandgap of a host included in each of the first ETL816 and the N-type CGL 841. The energy bandgap of the first ETL 816 maybe configured 0.50 eV higher than an energy bandgap of a host includedin the N-type CGL 841. That is, the energy bandgap of the first ETL 816may be configured 0.50 eV to 1.00 eV higher than the energy bandgapincluded in the N-type CGL 841. Also, the first ETL 816 may besubstantially the same as the first ETL 516 described above withreference to FIG. 11, and thus, its detailed description is omitted.

The first and second ECLs 813 and 823 may be provided in at least oneamong the first emission part 810 and the second emission part 820.Also, the first and second ECLs 813 and 823 may be disposed under thefirst EML 814 and the second EML 824.

The ECL 813 may be provided in an emission part including the first ETL816 having an energy bandgap shifted higher than that of a host includedin the CGL 840. Therefore, provided is an organic light emitting displaydevice in which a balance of electrons and holes is adjusted in thefirst EML 814, lifetime is stably reduced as time elapses, and lifetimeis long. That is, if the first ETL 816 and the first ECL 813 are allprovided, lifetime is further enhanced, and lifetime linearly changeswithout being changed to a bell shape as time elapses, thereby providingan organic light emitting display device having long lifetime.

Moreover, the second ECL 823 may be formed of two materials which havedifferent absolute values in LUMO energy level, and may be provided inan emission part including the second ETL 826 formed of two materials.Therefore, provided is an organic light emitting display device in whicha balance of electrons and holes is adjusted in the second EML 824,lifetime is stably reduced as time elapses, and lifetime is long. Thatis, if the second ETL 826 and the second ECL 823 are all provided,lifetime is further enhanced, and lifetime linearly changes withoutbeing changed to a bell shape as time elapses, thereby providing anorganic light emitting display device having long lifetime.

A driving voltage, efficiency, and lifetime in the eighth embodiment ofthe present disclosure will be described below with reference to thefollowing Table 3 and FIG. 17.

The following Table 3 shows a result obtained by measuring a drivingvoltage, efficiency, and color coordinates in a comparative example 2and the seventh and eighth embodiments of the present disclosure.

TABLE 3 Driving Efficiency Voltage (V) (cd/A) CIEx CIEy Comparative 7.311.8 0.135 0.068 Example 2 Experiment 7.6 10.9 0.135 0.068 Example 8Experiment 7.4 13.5 0.135 0.068 Example 9

In Table 3, the comparative example 2 has been experimented by applyingthe organic light emitting device of FIG. 2.

The comparative example 2 is configured identically to the comparativeexample 1. In the comparative example 2, the first ETL 716 is formed ofa material where a difference between an energy bandgap of the first ETL716 and an energy bandgap of a host included in the N-type CGL 741 is0.40 eV.

The experiment example 8 corresponds to the seventh embodiment of thepresent disclosure and is configured identically to the experimentexample 7. In the experiment example 8, the first ETL 716 is formed of amaterial where the difference between the energy bandgap of the firstETL 716 and the energy bandgap of the host included in the N-type CGL741 is 0.50 eV.

The experiment example 9 corresponds to the eighth embodiment of thepresent disclosure and is configured identically to the seventhembodiment of the present disclosure. In the experiment example 9, thefirst ECL 813 is formed before forming the first EML 814 in a redsubpixel area, a green subpixel area, and a blue subpixel area.

In Table 3, color coordinates (CIEx, CIEy) represent blue colorcoordinates (0.135, 0.068). Table 3 shows a result that is obtained bycomparing the driving voltages (V) and the efficiencies (cd/A) withrespect to a current density of 5 mA/cm² in a state where the blue colorcoordinates are identically set.

To describe the driving voltages (V), as shown in Table 3, it can beseen that in the driving voltages (V), the experiment example 8increases a little in comparison with the comparative example 2 and theexperiment example 9.

To describe the efficiencies (cd/A), since an ECL is further provided inan ETL, it can be seen that the experiment example 9 corresponding tothe eighth embodiment of the present disclosure is enhanced further inefficiency than the experiment example 8 corresponding to the seventhembodiment of the present disclosure. That is, it can be seen thatefficiency is further enhanced in a case where the first ETL 816 isconfigured so that a difference between an energy bandgap of the firstETL 816 and an energy bandgap of a host included in the N-type CGL 841is 0.50 eV or more and the ECL is further provided.

Lifetime will be described below with reference to FIGS. 16 and 17. Alifetime measurement result shown in each of FIGS. 16 and 17 has beenobtained through measurement for an experiment, and a measured lifetimedoes not limit details of the present disclosure. Therefore, FIGS. 16and 17 show results obtained measuring lifetime for checking whetherlifetime is enhanced under conditions of the experiment example 8corresponding to the seventh embodiment of the present disclosure andthe experiment example 9 corresponding to the eighth embodiment of thepresent disclosure.

FIG. 16 is a diagram showing lifetimes in the comparative example 2 andthe experiment example 8 of the present disclosure.

In FIG. 16, the abscissa axis indicates time (hr), and the ordinate axisindicates a luminance drop rate (%). Also, the comparative example 2 isreferred to as a2, and the experiment example 8 is referred to as H.

As shown in FIG. 16, when initial emission luminance is 100%, it can beseen that in time (i.e., a 95% lifetime (T95) of the organic lightemitting device) taken until luminance is reduced by 95%, thecomparative example 2 is about 320 hours, and the experiment example 8is about 380 hours. Therefore, it can be seen that the lifetime of theexperiment example 8 corresponding to the seventh embodiment of thepresent disclosure increases by about 1.2 times lifetime of thecomparative example 2. That is, it can be seen that efficiency isfurther enhanced in the seventh embodiment of the present disclosure,where the first ETL 716 is configured so that a difference between anenergy bandgap of the first ETL 716 and an energy bandgap of a hostincluded in the N-type CGL 741 is 0.50 eV or more, than the comparativeexample 2.

Moreover, FIG. 16 shows blue lifetime, and a total lifetime of theorganic light emitting display device is enhanced further in theexperiment example 8 than the comparative example 2.

FIG. 17 is a diagram showing lifetimes in the comparative example 2 andthe experiment example 9 of the present disclosure.

In FIG. 17, the abscissa axis indicates time (hr), and the ordinate axisindicates a luminance drop rate (%). Also, the comparative example 2 isreferred to as a2, and the experiment example 9 is referred to as I.

As shown in FIG. 17, when initial emission luminance is 100%, it can beseen that in time (i.e., a 95% lifetime (T95) of the organic lightemitting device) taken until luminance is reduced by 95%, thecomparative example 2 is about 320 hours, and the experiment example 9corresponding to the eighth embodiment of the present disclosure isabout 700 hours. Therefore, it can be seen that the lifetime of theeighth embodiment of the present disclosure increases by about 2.2 timeslifetime of the comparative example 2. That is, it can be seen thatefficiency is further enhanced in the eighth embodiment of the presentdisclosure, where the first ETL 816 is configured so that a differencebetween an energy bandgap of the first ETL 816 and an energy bandgap ofa host included in the N-type CGL 841 is 0.50 eV or more and the ECL isprovided, than the comparative example 2.

Moreover, FIG. 17 shows blue lifetime, and a total lifetime of theorganic light emitting display device is enhanced further in theexperiment example 9 than the comparative example 2.

Through such a result, it can be seen that lifetime is enhanced furtherin the seventh embodiment of the present disclosure, where the first ETL716 is configured so that a difference between an energy bandgap of thefirst ETL 716 and an energy bandgap of a host included in the N-type CGL741 is 0.50 eV or more, the second ETL 726 is formed of at least twomaterials having different absolute values of LUMO energy levels, andthe ECL 723 is provided, than the comparative example 2 where adifference between an energy bandgap of the first ETL 716 and an energybandgap of a host included in the N-type CGL 741 is 0.40 eV. Also, incomparison with the second embodiment of the present disclosure, it canbe seen that in the seventh embodiment of the present invention, as timeelapses, lifetime is not changed to a bell shape but becomes linear,namely, lifetime is improved.

Moreover, it can be seen that lifetime is enhanced further in the eighthembodiment of the present disclosure, where the first ETL 816 isconfigured so that a difference between an energy bandgap of the firstETL 816 and an energy bandgap of a host included in the N-type CGL 841is 0.50 eV or more, the first ECL 813 is provided, and the second ETL826 is formed of at least two materials having different absolute valuesof LUMO energy levels, and the second ECL 823 is provided, than thecomparative example 2. That is, an organic light emitting display devicewhere lifetime is not reduced despite the elapse of time is provided.

If the organic light emitting device according to the second to eighthembodiments of the present disclosure is applied to an organic lightemitting display device, a display device including three pixels (forexample, a red pixel, a green pixel, and a blue pixel) which eachinclude a monocolor device may be implemented. Therefore, a displaydevice which combines three primary colors of RGB to express variouscolors may be implemented. Also, the organic light emitting deviceaccording to the second to eighth embodiments of the present disclosuremay be applied to a bottom emission display device, a top emissiondisplay device, a dual emission display device, a lighting device forvehicles, and/or the like. The lighting device for vehicles may be atleast one among headlight, a high beam, taillight, a brake light, aback-up light, a fog lamp, a turn signal light, and an auxiliary lamp,but is not limited thereto. Alternatively, the organic light emittingdisplay device including the organic light emitting device according tothe second to eighth embodiments of the present disclosure may beapplied to all indicator lamps which are used to secure a field of viewof a driver and transmit or receive a signal of a vehicle. Also, theorganic light emitting display device including the organic lightemitting device according to the second to eighth embodiments of thepresent disclosure may be applied to mobile equipment, monitors,televisions (TVs), and/or the like.

As described above, an ETL according to the embodiments of the presentdisclosure may be configured so that an absolute value of a LUMO energylevel of a first material is greater than an absolute value of a LUMOenergy level of a second material and a content of the second materialis higher than that of the first material, and thus, an emission areamay be located in an EML, thereby providing an organic light emittingdisplay device with enhanced lifetime.

Moreover, an ETL according to the embodiments of the present disclosuremay be configured so that an absolute value of a LUMO energy level of afirst material is greater than an absolute value of a LUMO energy levelof a second material and a content of the second material is higher thanthat of the first material, and an ECL may be formed. Accordingly, anemission area of an EML is enlarged as time elapses, thereby providingan organic light emitting display device in which lifetime is steadilyreduced as time elapses.

Moreover, according to the embodiments of the present disclosure, sincean energy bandgap of an ETL is adjusted higher than an energy bandgap ofa host included in a CGL, an emission area is located in an EML, therebyproviding an organic light emitting display device with enhancedlifetime.

Moreover, according to the embodiments of the present disclosure, sincean energy bandgap of an ETL is adjusted higher than an energy bandgap ofa host included in a CGL and an ECL is provided, an emission area of anEML is enlarged as time elapses, thereby providing an organic lightemitting display device in which lifetime is steadily reduced as timeelapses.

Moreover, according to the embodiments of the present disclosure, sinceone of two ETLs is configured so that an absolute value of a LUMO energylevel of a first material of an ETL is larger than an absolute value ofa LUMO energy level of a second material and a content of the secondmaterial is higher than that of the first material, an ECL is provided,and the other of the two ETLs is configured so that an energy bandgap ofan ETL is adjusted higher than an energy bandgap of a host included in aCGL, an emission area is located in an EML, thereby providing an organiclight emitting display device with enhanced lifetime.

Moreover, according to the embodiments of the present disclosure, sinceone of two ETLs is configured so that an absolute value of a LUMO energylevel of a first material of an ETL is larger than an absolute value ofa LUMO energy level of a second material and a content of the secondmaterial is higher than that of the first material, the other of the twoETLs is configured so that an energy bandgap of an ETL is adjustedhigher than an energy bandgap of a host included in a CGL, and an ECL isprovided, an emission area of an EML is enlarged as time elapses,thereby providing an organic light emitting display device in whichlifetime is stably reduced as time elapses.

An organic light emitting display device according to an embodiment ofthe present disclosure may include an anode on a substrate, a firstemission part that is disposed on the anode and includes a firstemission layer and a first electron transfer layer, a second emissionpart that is disposed on the first emission part and includes a secondemission layer and a second electron transfer layer, and a cathode onthe second emission part. At least one among the first electron transferlayer and the second electron transfer layer may include a firstmaterial and a second material, and an absolute value of a LUMO energylevel of the first material may be larger than an absolute value of aLUMO energy level of the second material.

A content of the second material may be adjusted higher than a contentof the first material.

In the first electron transfer layer or the second electron transferlayer, a content of the second material may be more than 50 wt %.

The first material and the second material may be mixed throughco-deposition.

The absolute value of the LUMO energy level of the first material may bewithin a range of 2.91 eV to 3.40 eV, and the absolute value of the LUMOenergy level of the second material may be within a range of 2.60 eV to2.90 eV.

The first electron transfer layer may include one among the firstmaterial and the second material, and the second electron transfer layermay include the first material and the second material.

The organic light emitting display device may further include a secondhole transfer layer on the first electron transfer layer and a secondemission control layer between the second hole transfer layer and thesecond emission layer.

An absolute value of a HOMO energy level of the second emission controllayer may be 0.10 eV to 0.50 eV larger than an absolute value of a HOMOenergy level of the second hole transfer layer.

A hole mobility of the second emission control layer may be 1.0×10⁻¹ to1.0×10⁻² times lower than a hole mobility of the second hole transferlayer.

The first electron transfer layer and the second electron transfer layermay each include the first material and the second material.

The organic light emitting display device may further include a firsthole transfer layer on the anode and a first emission control layerbetween the first hole transfer layer and the first emission layer.

An absolute value of a HOMO energy level of the first emission controllayer may be 0.10 eV to 0.50 eV larger than an absolute value of a HOMOenergy level of the first hole transfer layer.

A hole mobility of the first emission control layer may be 1.0×10⁻¹ to1.0×10⁻² times lower than a hole mobility of the first hole transferlayer.

The organic light emitting display device may further include a secondhole transfer layer on the first electron transfer layer and a secondemission control layer between the second hole transfer layer and thesecond emission layer.

An absolute value of a HOMO energy level of the second emission controllayer may be 0.10 eV to 0.50 eV larger than an absolute value of a HOMOenergy level of the second hole transfer layer.

A hole mobility of the second emission control layer may be 1.0×10⁻¹ to1.0×10⁻² times lower than a hole mobility of the second hole transferlayer.

The second electron transfer layer may include the first material andthe second material.

The organic light emitting display device may further include an N-typecharge generation layer between the first emission part and the secondemission part, and the first electron transfer layer may include amaterial having an energy bandgap which is 0.50 eV to 1.00 eV higherthan an energy bandgap of a host included in the N-type chargegeneration layer.

An absolute value of a LUMO energy level of the first electron transferlayer may be within a range of 2.00 eV to 2.50 eV, and an absolute valueof a LUMO energy level of the N-type charge generation layer may bewithin a range of 2.90 eV to 3.20 eV.

The organic light emitting display device may further include anemission control layer under at least one of the first emission layerand the second emission layer.

The first emission layer and the second emission layer may emit lighthaving the same color.

An organic light emitting display device according to an embodiment ofthe present disclosure may include an anode on a substrate, a firstemission part that is disposed on the anode and includes a first holetransfer layer, a first emission layer, and a first electron transferlayer, a second emission part that is disposed on the first emissionpart and includes a second hole transfer layer, a second emission layer,and a second electron transfer layer, and a cathode on the secondemission part. At least one among the first emission part and the secondemission part may include an emission control layer having an absolutevalue of a HOMO energy level which is larger than an absolute value of aHOMO energy level of the first hole transfer layer or the second holetransfer layer.

An absolute value of a HOMO energy level of the emission control layermay be 0.10 eV to 0.50 eV larger than an absolute value of a HOMO energylevel of the first hole transfer layer or the second hole transferlayer.

A hole mobility of the emission control layer may be 1.0×10⁻¹ to1.0×10⁻² times lower than a hole mobility of the first hole transferlayer or the second hole transfer layer.

The second electron transfer layer may include at least two materials,and a material having a small absolute value of a LUMO energy levelamong the at least two materials may be higher in content than anothermaterial having a large absolute value of the LUMO energy level amongthe at least two materials.

The emission control layer may be provided in the second emission partand between the second hole transfer layer and the second emissionlayer.

The first electron transfer layer may include one among the at least twomaterials.

The first electron transfer layer and the second electron transfer layermay each include at least two materials, and a material having a smallabsolute value of a LUMO energy level among the at least two materialsmay be higher in amount than another material having a large absolutevalue of the LUMO energy level among the at least two materials.

The emission control layer may be provided in the first emission partand the second emission part, between the first hole transfer layer andthe first emission layer, and between the second hole transfer layer andthe second emission layer.

The organic light emitting display device may further include an N-typecharge generation layer between the first emission part and the secondemission part, and the first electron transfer layer may include amaterial having an energy bandgap which is 0.50 eV to 1.00 eV higherthan an energy bandgap of a host included in the N-type chargegeneration layer.

The emission control layer may be provided in the first emission partand between the first hole transfer layer and the first emission layer.

The second electron transfer layer may include at least two materials,and a material having a small absolute value of a LUMO energy levelamong the at least two materials may be higher in content than anothermaterial having a large absolute value of the LUMO energy level amongthe at least two materials.

The emission control layer may be provided in the second emission partand between the second hole transfer layer and the second emissionlayer.

The first electron transfer layer may include one among anthracenederivatives, triazine derivatives, and carbozole derivatives.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present disclosurewithout departing from the spirit or scope of the disclosures. Thus, itis intended that the present disclosure covers the modifications andvariations of this disclosure provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. An organic light emitting display device,comprising: an anode on a substrate; a first emission part on the anode,the first emission part including a first emission layer and a firstelectron transfer layer; a second emission part on the first emissionpart, the second emission part including a second emission layer and asecond electron transfer layer; an N-type charge generation layerbetween the first emission part and the second emission part; and acathode on the second emission part, wherein at least one among thefirst electron transfer layer and the second electron transfer layercomprises a first material and a second material, and an absolute valueof a lowest unoccupied molecular orbital (LUMO) energy level of thefirst material is larger than an absolute value of a LUMO energy levelof the second material, wherein the first material has an absolute valueof the LUMO energy level within a first range of 2.91 eV to 3.40 eV andthe second material has an absolute value of the LUMO energy levelwithin a second range of 2.60 eV to 2.90 eV, wherein the first range andthe second range do not overlap, wherein the first electron transferlayer comprises one among the first material and the second material,and the second electron transfer layer comprises the first material andthe second material, and wherein a difference between a LUMO energylevel of the first electron transfer layer and a LUMO energy level ofthe N-type charge generation layer is 0.50 eV to 1.00 eV.
 2. The organiclight emitting display device of claim 1, wherein an amount of thesecond material is higher than an amount of the first material.
 3. Theorganic light emitting display device of claim 1, wherein in the firstelectron transfer layer or the second electron transfer layer, a contentof the second material is more than 50 wt %.
 4. The organic lightemitting display device of claim 1, wherein the first material and thesecond material are mixed through co-deposition.
 5. The organic lightemitting display device of claim 1, further comprising: a second holetransfer layer on the first electron transfer layer; and a secondemission control layer between the second hole transfer layer and thesecond emission layer.
 6. The organic light emitting display device ofclaim 5, wherein an absolute value of a highest occupied molecularorbital (HOMO) energy level of the second emission control layer is 0.10eV to 0.50 eV larger than an absolute value of a HOMO energy level ofthe second hole transfer layer.
 7. The organic light emitting displaydevice of claim 5, wherein a hole mobility of the second emissioncontrol layer is 1.0×10⁻¹ to 1.0×10⁻² times lower than a hole mobilityof the second hole transfer layer.
 8. The organic light emitting displaydevice of claim 1, wherein the first electron transfer layer comprisesthe first material and the second material.
 9. The organic lightemitting display device of claim 8, further comprising: a first holetransfer layer on the anode; and a first emission control layer betweenthe first hole transfer layer and the first emission layer.
 10. Theorganic light emitting display device of claim 9, wherein an absolutevalue of a highest occupied molecular orbital (HOMO) energy level of thefirst emission control layer is 0.10 eV to 0.50 eV larger than anabsolute value of a HOMO energy level of the first hole transfer layer.11. The organic light emitting display device of claim 9, wherein a holemobility of the first emission control layer is 1.0×10⁻¹ to 1.0×10⁻²times lower than a hole mobility of the first hole transfer layer. 12.The organic light emitting display device of claim 8, furthercomprising: a second hole transfer layer on the first electron transferlayer; and a second emission control layer between the second holetransfer layer and the second emission layer.
 13. The organic lightemitting display device of claim 12, wherein an absolute value of ahighest occupied molecular orbital (HOMO) energy level of the secondemission control layer is 0.10 eV to 0.50 eV larger than an absolutevalue of a HOMO energy level of the second hole transfer layer.
 14. Theorganic light emitting display device of claim 12, wherein a holemobility of the second emission control layer is 1.0×10⁻¹ to 1.0×10⁻²times lower than a hole mobility of the second hole transfer layer. 15.The organic light emitting display device of claim 1, wherein anabsolute value of the LUMO energy level of the first electron transferlayer is within a range of 2.00 eV to 2.50 eV, and an absolute value ofthe LUMO energy level of the N-type charge generation layer is within arange of 2.90 eV to 3.20 eV.
 16. The organic light emitting displaydevice of claim 1, further comprising: an emission control layer underat least one of the first emission layer and the second emission layer.17. The organic light emitting display device of claim 1, wherein thefirst emission layer and the second emission layer emit light having thesame color.
 18. The organic light emitting display device of claim 1,wherein a ratio of the first material and the second material is 1:1 inwt %.
 19. An organic light emitting display device, comprising: an anodeon a substrate; a first emission part on the anode, the first emissionpart including a first hole transfer layer, a first emission layer, anda first electron transfer layer; a second emission part on the firstemission part, the second emission part including a second hole transferlayer, a second emission layer, and a second electron transfer layer; anN-type charge generation layer between the first emission part and thesecond emission part; and a cathode on the second emission part, whereinat least one among the first emission part and the second emission partcomprises an emission control layer having an absolute value of ahighest occupied molecular orbital (HOMO) energy level which is largerthan an absolute value of a HOMO energy level of the first hole transferlayer or the second hole transfer layer, wherein at least one among thefirst electron transfer layer and the second electron transfer layerincludes at least two materials that are mixed through co-deposition,wherein a first material of the at least two materials has an absolutevalue of a lowest unoccupied molecular orbital (LUMO) energy levelwithin a first range of 2.91 eV to 3.40 eV and a second material of theat least two materials has an absolute value of a lowest unoccupiedmolecular orbital (LUMO) energy level within a second range of 2.60 eVto 2.90 eV, wherein the first range and the second range do not overlap,wherein the first electron transfer layer comprises one among the atleast two materials, and the second electron transfer layer comprisesthe at least two materials, and wherein a difference between a LUMOenergy level of the first electron transfer layer and a LUMO energylevel of the N-type charge generation layer is 0.50 eV to 1.00 eV. 20.The organic light emitting display device of claim 19, wherein theabsolute value of the HOMO energy level of the emission control layer is0.10 eV to 0.50 eV larger than the absolute value of the HOMO energylevel of the first hole transfer layer or the second hole transferlayer.
 21. The organic light emitting display device of claim 19,wherein a hole mobility of the emission control layer is 1.0×10⁻¹ to1.0×10⁻² times lower than a hole mobility of the first hole transferlayer or the second hole transfer layer.
 22. The organic light emittingdisplay device of claim 19, wherein a material having a small absolutevalue of the LUMO energy level among the at least two materials ishigher in amount than another material having a large absolute value ofthe LUMO energy level among the at least two materials.
 23. The organiclight emitting display device of claim 22, wherein the emission controllayer is provided in the second emission part and between the secondhole transfer layer and the second emission layer.
 24. The organic lightemitting display device of claim 19, wherein each of the first electrontransfer layer and the second electron transfer layer comprises the atleast two materials, and a material having a small absolute value of theLUMO energy level among the at least two materials is higher in amountthan another material having a large absolute value of the LUMO energylevel among the at least two materials.
 25. The organic light emittingdisplay device of claim 24, wherein the emission control layer isprovided in the first emission part and the second emission part,between the first hole transfer layer and the first emission layer, andbetween the second hole transfer layer and the second emission layer.26. The organic light emitting display device of claim 19, wherein theemission control layer is provided in the first emission part andbetween the first hole transfer layer and the first emission layer. 27.The organic light emitting display device of claim 19, wherein theemission control layer is provided in the second emission part andbetween the second hole transfer layer and the second emission layer.28. The organic light emitting display device of claim 19, wherein thefirst electron transfer layer comprises one among anthracenederivatives, triazine derivatives, and carbozole derivatives.
 29. Theorganic light emitting display device of claim 19, wherein a ratio ofthe first material and the second material is 1:1 in wt %.